Worship of shivalinga is considered the prime worship for the devotees of Lord shiva. Worship of all other forms is considered secondary. The significance of the shivalinga is that It is the resplendent light (flame) form of the Supreme - solidified to make the worship of It easier. It represents the real nature of God - formless essentially and taking various forms as It wills.
This jyoti swarUpa of God exist in all the shivalinga forms, there are prominent abodes across Indian subcontinent, where It is in a splendid form. These are renowned as dvAdasa jyotir lingas or 12 jyotirlingas. These are held at much great esteem since the ancient pre-historic times. purANas talk in many sections as well as in detail about the glory of these abodes. Devotees have been getting pulled towards these kshetras due to the highly benevolent divine presence in these abodes, since ancient times.
The 12 jyotirlinga temples
There is an sanskrit shloka that lists the twelve jyotirlinga temples.
"Saurashtre Somanathamcha Srisaile Mallikarjunam|
Ujjayinya Mahakalam Omkaramamaleswaram ||
Paralyam Vaidyanathancha Dakinyam Bheema Shankaram |
Setu Bandhethu Ramesam, Nagesam Darukavane||
Varanasyantu Vishwesam Tryambakam Gautameethate|
Himalayetu Kedaaram, Ghrishnesamcha shivaalaye||
Etani jyotirlingani, Saayam Praatah Patennarah|
Sapta Janma Kritam pApam, Smaranena Vinashyati||"
Mahadev, the Lord incorporates in Himself, the aura and the holiness of all the twelve JyotirLingas. The grandeur of these places is unique. Devotees line up in great numbers to take a look and get a Darshan of all the JyotirLingas.
Location of the jothirlinga temples
Two on the sea shore, three on river banks, four in the heights of the mountains and three in villages located in meadows; the twelve Jyotirlingas are spread out like this. Every place has been described in glorious words by many detailing the surroundings etc.
Those of us who go to these temples of Shubhankar Shankar- Jyoti-Sivasthan, receive the holy blessings of the Lord, and come back happy, peaceful and blessed. This in indeed depends on one's devotion and experience too.
1. Somnath Temple, Gujrat (Lord Somnath)
Somnath is probably one of the most famous temples in India both due to legend and history. Considered one of the first Jyotirlingas, Shiva was worshipped at Somnath by different names such as Mrityunjaya (one who has conquered death), Kalagnirudra and Bhairavanatha. As per the various texts of Hinduism such as the Skanda purana, the Moon or Chandra was married to the 27 daughters of Daksha prajapati, the son of Brahma and one of the prajapati's on earth. As it happened, Chandra/Moon loved his wife Rohini more than the rest of her sisters. The furiously angry wives went to their father Daksha and complained about their condition to him. Daksha was primarily known for his uncontrollable temper and he summoned Rohini and Chandra to his presence. After having confirmed the truth in the complaint, Daksha promptly cursed Chandra such that his illustrous light and face be reduced to nothing. From the curse, Chandra became lusterless and withered away with time. Chandra's 27 wives were alarmed with their father's curse and bade him to diminish it. A curse once uttered could not be taken back but it could be modified and so Daksha decreed that Chandra would was and wane periodically. But his lustre was still missing. So, legend has it that Chandra, burdened with Daksha's curse, turned to Lord Shiva and prayed to him at Somnath. Lord Shiva appeared in front of Chandra in due time 
and blessed him with an illustrous form for half of his time during the month. Since the moon regained his illumination at this spot, the name Somnath and Prabhasa came into being. It is not clear as to who first had the temple of Somnath built. Legend tells us that Brahma the creator himself built it. Some historic sources mention that Bhimdev Solanki, the then ruler of Gujrat had it built. But history does mention Somnath several times during the centuries. The wealth of Somnath was legendary; something that was confirmed by Al Beruni the Arab traveller himself in his writings on Travels in India. Unfortunately for Somnath, its riches and wealth attracted several Islamic invaders such as Muhmud Ghazni (at least twice), all the way to Aurangzeb. The temple of Somnath is said to have been rebuilt seven times. Legend has it that when Mahmud Ghazni sacked Somnath, he personally broke the Jyotirlingam in the temple and the broken pieces were taken to Ghazni where they were incorporated into the stone steps of the Jama Masjid. While several legends revolve around the sacking of Somnath, historic sources do provide us with the facts that the temple itself was built in different periods through history from Pratiharas to the Chalukyas to the latest version which was built in 1947 by Sardar Vallabhai Patel. Somnath is perhaps the most famous of all the twelve Jyotirlingams, seeped both in legend and history.
2. Srisailam Temple, Kurnool, Andhra Pradesh (Lord Mallikarjuna and Bhramaramba Devi)
Srisailam is located in the midst of the Nallamalai hills near Kurnool in Andhra Pradesh. Dedicated to Shiva as Lord Mallikarjuna and Parvati as Bhramaramba Devi, Srisailam is the only temple with one of the twelve Jyotirlingams and one of the 18 Mahashaktis located in the same temple compound. As temples go, Srisailam is a really old temple and is mentioned in several ancient Hindu texts and by Ancient Tamil poets called the Alwars. The temple itself is surrounded by dense forests and in ancient times, pilgrimage to Srisailam made a very dangerous journey. Legend has it that the bull of Shiva by name Vrishabha did penance at this exact spot. In answer to his prayers, Shiva and Parvati appeared in the form of Lord Mallikarjuna and Devi Bhramaramba. There are several other fascinating legends regarding Srisailam. 
It is said that the lingam was originally placed in its location by Lord Rama. It is also said that the five Pandavas placed five lingams in the courtyard. Srisailam is mentioned even in the Mahabharata. Even Hiranyakashapu, the fabled king of the Asuras is said to have performed pujas at this temple. One of the most interesting legends revolving around the Srisailam temple talks of how Parvati defeated the demon Mahishasura in the form of a bee. As if to illustrate the reality in the legend, a tiny hole in the sanctum sanctorum of the temple causes a buzzing noise not unlike that of a bee. Architecturally, Srisailam is a true dravidian temple with its gopuram or tower built with smaller stories or pavillions.The temple itself shows distinct influences of the Kakatiya and Vijayanagar dynasties. King Krishnadeva Raya of Vijayanagaram is said to have contributed heavily towards the temple. Famous throughout the ages, the saint Adi Shankaracharya is said to have visited Srisailam and composed his divine hymn Sivananda Lahiri. Even the Maratha King Sivaji is said to have had a gopuram built in 1667 A.D. Today, Srisailam is a major pilgrimage site in Andhra Pradesh.
3. Kashi Vishwanath Temple (Lord Vishwanath and Devi Annapurna Visalakshi)
Considered the holiest city in India since time immemorial, Kashi continues to be the seat of Hinduism. Of all the Jyotirlinga temples in India, Kashi Vishwanath is perhaps the most famous of all. Built on the bank of the river Ganges; the holiest of all the rivers in Hinduism, the Kashi Vishwanath temple is considered to bless a pilgrim with Moksha or liberation. Legend holds that the fifth head of Brahma stuck hard to Shiva's palm and that it came off loose only at Varanasi. Another legend tells us how Sati's left palm is said to have fallen at Kaashi. Like Srisailam, Kaashi Viswanath is also a very unique temple since it contains not only one of the 12 Jyotirlingas of Shiva but also one of the 18 temples for the Goddess Shakti in the form of Annapurna Visalakshi. A very famous tradition in the Hindu marriage is named Kashi prasthanam wherein the bridegroom pretends to go off to Kashi and is persuaded by the bride's relatives to stay back and marry the bride. This tradition is set to have its roots in the legend of Shiva where Shiva, once hungry for food decided to beg for it in the true manner of a sanyasi. Shiva's consort Parvati is said to have taken the form of Annapura (The goddess of food often pictured with a ladle in hand) and is said to have assuaged his hunger. Historically, the Vishweshwara or Vishwanath temple has been demolished several times by islamic rulers and invaders. However, like Somnath, the temple has been rebuilt painstakingly each time. The original temple is said to have been built about 3500 years ago and is of unknown origin. The latest temple however is said to have been built by Ahilya Bai Holker, the maharani of Indore in 1780. Several historic names have been associated with the temple. Akbar, India's most famous Mughal emperor is said to have given permission to the Hindu community to rebuild the temple during his time only to be demolished by his great grandson Aurangzeb in his religious zeal. Aurangzeb had the temple demolished and had a mosque built on the spot. The mosque and the new temple lie side by side to this day. It is said that the Kashi Viswanath temple contains a well which was used to hide the sacred Lingam from any invasion. Another fascinating custom is observed during the festival of Shivratri when the deity is worshipped by the King of Kashi and nobody else is allowed to view the puja or the Lingam during this time. The dome of the temple is made of pure gold leaf and is said to have been contributed by Maharaja Ranjit Singh of Punjab. Several saints and philosophers have visited the Viswanath temple and they include Adi Shankaracharya, Swami Viviekananda, Guru Nanak, Tulsidas, Ramakrishna Paramahansa. It is interesting to note that despite several invasions and acts of demolition, the Kashi Vishwanath temple is still one of the most popular temples in the Indian subcontinent.
4. Omkareshwar Temple, Madhya Pradesh (Lord Omkareshwara) 
Omkareshwar temple is located on the banks of the river Narmada. Legend has it that the island on which the temple is located was originally shaped as the holy letter Om and hence the temple was named Omkareshwar. The hamlet of Mandhata has two famous temples of Shiva. The first temple is Omkareshwar which is considered one of the twelve divine Jyotirlingas. The second temple is called Amareshwar since Shiva is also known as Amareshwara or the immortal one. Several legends exist around Omkareshwar. Some believe that Mount Vindhya prayed to Shiva at this spot and was granted his wish. The holy spot came to be known as Omkareshwar. Others believe that the shiva linga at Mandhata split into two. One half became the linga at Omkareshwar while the other half became the linga at Amareshwar. Either ways, Omkareshwar is not without its share of beauty or fame. The guru of Adi Shankaracharya was set have resided in a cave near the temple. The temple architecture is unique and the huge Shikara is said to have been built in the Nagara style. As per the Nagara style, the Gopuram or the tower is built in the beehive form.
5. Kedarnath Temple, Utterakand (Lord Kedarnath)
Kedarnath Temple is the northernmost Jyotirlinga temple in India. Located 12000 feet above the sea level in the Himalayas, the temple is accessible only for six months in the summer. The temple is located near the Mandakini river and there is no clear evidence as to who originally built it. Legend tells us that Adi Shankaracharya, 
the saint had it built and to support this tale, a temple dedicated to the saint's samadhi is also located close by to the Kedarnath Temple. Kedarnath is one of the Char Dham temples of India. The entire temple is built from stone and is very different in its architecture to the other Jyotirlinga temples. Several Legends a bout Kedarnath prevail. Legend has it that the temple is located in the Rudra Himalaya peak where the five pandavas are set to have died. After the battle of Kurukshetra, the five pandavas visited Kedarnath in order to worship Lord Shiva who having seen them approaching the temple decided to take the form of a buffalo and then hide under the ground. Five portions of the buffalo's body were uncovered and together they form the Pancha Kedara temples. Arjuna, the third Pandava is also credited to have recieved the Pasupataastra at Kedarnath after his prayers. Bhima, Arjuna's brother is said to have had his legendary meeting with Hanuman (his elder brother) at Kedarnath after having searched for the divine flowers that Draupadi requested. According to tradition, Parvati prayed to the Lord Kedareshwar in order to be united to him. The boon was granted and thus, from that union emerged Ardhanareshwara, half Shiva and half Parvati. The temple was also built on the site where Nara and Narayana were supposed to have prayed to Lord Shiva and asked him to stay on Earth in the form of a Jyotirlinga. Kedarnath is full of traditions. Pilgrims visiting Kedarnath usually arrive at the temple only after visiting and bringing with them the holy waters of Yamunotri and Gangotri.
6. Mahakaleshwar Temple, Ujjain, (Lord Mahakaleshwara)
Ujjain is a very ancient city. During ancient times, it was considered to be the capital city of the kingdom of Avanti. One of its most famous kings was King Vikramaditya of the Gupta dynasty. The court of Vikramaditya was famous for its nine gems; personages of great talent who included Kalidasa the famous poet. The Kumbh Mela is also held at Ujjain making it a very important pilgrimage spot. As per the local legend a demon named Dushana created chaos in the kingdom of Avanti and the people prayed to Shiva to rescue them from the torment of the demon. Shiva obliged and killed the demon and then chose to stay in Ujjain in the form of the Jyotirlinga called Mahakaleshwara. There are several unique features of Mahakaleshwar that distinguish it from the remaining Jyotirlingams. 
The Jyotirlinga at Mahakaleshwar is a swayambhu or self born Linga. The Linga is also a south facing lingam and hence is refered to by the name Dakshinamurthy. This is the only Lingam amongst the twelve Jyotirlingas to have this attribute and the temple is a five storied structure with an idol of Shiva or his consort or sons adorning each level. In the basement level is said to be the deity Nagachandreshwar which is shown to public only during the sacred Nagapanchami day. The prasad offered to the Lingam at Mahakaleshwar can be re-offered to other deities, an outstanding feature considering that prasad once offered to a deity should never be offered to another deity. Pilgrims hold that a visit to the Mahakaleshwar linga ensures freedom from diseases and the fear of death. As temple architecture goes, the temple is situated on the shore of the lake Rudra Sagar. The gopuram or tower is built in the typical Nagara style seen in North India.
7. Bhimashankar, Pune (Lord Bhimashekara)
Bhimashankhar is one of the three Jyotirlingas located in the state of Maharasthra. Built on the banks of the Bhima river, the temple of Bhimashankar is a very ancient one. According to local legend, Tripurasura, a demon obtained a boon wherein he owned three citadels that were always floating around in the sky. As per his boon, Tripurasura was invincible as long as nobody destroyed the three citadels at once. After Tripurasura began harrassing mortals and celestial beings alike, Shiva is said to have fired an arrow through the three citadels that aligned together once every thousand years. Tripurasura was slain and Shiva who had taken the form of a Bhima was set to have sweated profusely, causing the Bhima river to be born. Since that time, a Jyotirlinga, endowed with the powers of Shiva has been worshipped at the spot. As north Indian temples go, Bhimashankar Temple is a bit of a mystery. There are some portions of the temple that are very old and some that are fairly new. The sanctum sanctorum is situated at a lower level as is common in Shivite temples. Shivaji and other Maratha chieftains are said to have contributed generously for the upkeep of this temple. Saint Jnaneshwar is said to have visited Bhimashankar. Today, Bhimashankar is one of the most important shrines in Maharasthra.
8. Tryambakeshwar, Nashik (Lord Tryambakeshwara)
Tryambakeshwar, located at what is claimed to be the source of the river Godavari is a very unique shrine. According to local legend, the sage Gautama and his wife Ahalya lived here peacefully. As a result of a boon from the God Varuna, Gautama was blessed with a bottomless pit in his hermitage where he could store grain and other required articles. This pit became a source of jealousy to the other ages who managed to let a cow into Gautama's hermitage. The sage was in a hurry to drive the cow away but due to unfortunate circumstances, the cow fell into the pit and perished. The death of a cow was a very serious matter from a religious perspective and Gautama prayed to Lord Shiva to allow Ganga to purify his hermitage of the sin. When Ganga arrived at the sage's hermitage, she was reborn as Godavari and Shiva took the form of Tryambaka. The legend is a very interesting one considering that the local population refers to the river as Ganga and not Godavari. The Tryambakeshwara Jyotirlinga is a very unique one. It is the only Jyotirlinga that has three faces attached to it. The first represents Brahma, the second represents Vishnu and the third represents Shiva. The lingam is quite small and is present close to the ground. Water constantly flows out from the top of the lingam. Tryambakeshwar Temple is unique since it is entirely built out of black stone. Its origins are unknown but history tells us that it underwent massive rennovation during the Maratha period. Tryambakeshwar is also a center for religious learning and several gurukuls were said to exist in the past.
9. Vaidyanath Temple, Deogarh, Jharkhand (Lord Vaidyanath)
The Vaidyanath Temple at Deogarh is perhaps the most controversial of all the Jyotirlinga temples. Essentially, there are several schools of thought that maintain that the Vaidyanath temple at Deogarh does not contain the Jyotirlinga but another temple, also known as the Vaidyanath temple in Parli is the original one. Whatever the facts show, the legend associated with the birth of the Vaidyanath temple is a very charming one. It is said that the Rakshasa king Ravana once prayed to Shiva at this spot. Shiva did not immediately appear in front of Ravana and this enraged the Rakshasa king who immediately decided to lift Mount Kailasa and take it with him to his citadel of Lanka. Shiva put a stop to Ravana's plans by pressing down hard with his little finger. Needless to say, Ravana almost got crushed under the mountain. Realizing his mistake, Ravana prayed to Shiva again and this time, the God appeared in front of his devotee, pleased at his devotion. Ravana asked for and obtained a Jyotirlinga from Shiva but the boon had a catch to it. The Jyotirlinga belonged to Ravana as long as it was not placed on the ground. once the Jyotirlinga touched the ground, it would instantly take root and would be immovable. Ravana set out to Lanka with the Jyotirlinga in his hand but when morning came, he had to go for his morning abultions and prayers at a nearby river. So, he handed the Jyotirlingam to a boy and bade him to hold it carefully until he returned from his prayers. The boy who in reality was Ganesha in disguise, placed the Jyotirlingam on the ground as soon as Ravana vanished from sight. When Ravana returned, he noted to his dismay that the Jyotirlingam was firmly planted on the ground and no amount of heaving would lift it up again. So, he chose to pray to Shiva once again and this time, as an offering, he chopped off nine of his ten heads. Shiva appeared before the distraught Ravana in the form of a vaidya (doctor) and then re-attached the heads back on. But Ravana lost the Jyotirlinga forever. A temple was then constructed around the Jyotirlingam and interestingly, one of the key features of the lingam is a tiny cleft on the top which is said to have come from Ravana's struggles to lift it. As north Indian temples go, nothing further is known about the temple itself. It is unknown as to who built it and the temple bears the typical Nagara gopuram seen in north indian temples. The temple is also marked by an enormous courtyard which is said to contain a well. The well as legend has it was built by Ravana and consecrated by the holy waters of all the holy rivers in India.
10. Nageshwar Temple, Dwarka (Lord Nageshwara)
Dwarka has been one of the most important pilgrimage centers in Hinduism since time immemorial. As per the puranas, Dwarka was the chosen capital of Krishna who established a yadava kingdom. The most famous temple in Dwarka is the Dwarkadhish temple dedicated to Krishna. However, not many people know that Dwarka is also the home of one of the twelve jyotirlingas of Shiva. The Nageshwar temple of Dwarka is the home to the jyotirlinga of Shiva worshipped as Lord Nageshwara. Legend has it that a demon by the name Daaruka attacked and imprisoned several devotees of Shiva including Supriya. In their imprisonment, Supriya suggested to the rest of her fellow prisoners that they chant and pray for Shiva. Shiva promptly appeared in the form of the Nageswara and killed the demon Daaruka with his Pasupatastra. A temple was built over the Jyotirlinga and it came to be known as the Nageshwar temple.
11. Grishneshwar Temple, Daulatabad (Lord Gusmeshwara)
Grishneshwar temple is considered to be very ancient. This temple is located near Daulatabad (once known as Devagiri) and was restored twice in history. According to legend, a devout woman by name Kusuma worshipped Shiva daily by immersing his lingam in the tank of water. Struck by jealousy, the first wife of Kusuma's husband murdered her son in front of her eyes. Though struck with sorrow, Kusuma continued to worship Shiva and the next time she immersed the lingam in water, her son came back to life. A temple was constructed on the spot for the Jyotirlingam which was worshipped as Lord Gusmeshwara. The temple follows the Nagara style of architecture seen in north Indian temples and was rennovated by the grandfather of Chatrapati Shivaji maharaj. Later on, it was demolished; probably on the orders of Aurangzeb. It was rebuilt again by Maharani Ahilya Bai Holker of Indore along with the Somnath and Kashi Vishwanath temple.
12. Rameshwaram Temple, Rameshwaram (Lord Rameshwara)
Rameshwaram is perhaps the most important shrine of Lord Shiva in south India. Along with the Kashi Vishwanath shrine in Varanasi, Rameshwaram is perhaps the main Shaivite temple in India. 
Legend tells us that Lord Rama worshipped Shiva on this spot after waging the battle with the Rakshasa King Ravana in Lanka. A victorious Rama is said to have requested Hanuman, the monkey God to go and fetch the sacred lingam from Kashi. As Hanuman was delayed, Sita is said to have shaped a beautiful lingam from the sand and Rama is said to have worhsipped this lingam. This lingam became the Jyotirlingam of Rameshwaram. When Hanuman returned with the lingam from Kashi, it was consecreted in the temple in the form of the Kashilingam or Hanumanlingam. Today, the priests always worship the Kashilingam prior to worshiping the Rameshwara lingam. As temples go, Rameshwaram is probably one of the most ornate and amazing examples of dravidian temple architecture. Built on a lavish 12 acre plot of land, Rameshwaram holds several records for Hindu temples. The massive temple complex is punctuated on four sides by massive gopurams. The entire temple is built of granite and there are several corridors that are 4000 feet long with 4000 pillars. The interesting fact about the granite is that the stone is not indegenous to Tamil Nadu and had to be brought in from elsewhere. The Sethupathy dynasty of Tamil Nadu is credited with the constructiona and upkeep of the temple although almost all of the royal houses in South India have contributed to the temple. The temple boasts 37 thirthams and also houses the shrine of Sethu Madhava; a form of Vishnu so called because of the white stone with which the statue was made. The temple complex of Rameshwaram also bears distince Pallava influence as well although Pandya rulers were said to have constructed it first. Today, Rameshwaram remains one of the most important pilgrimage sites for Shiva in south India.
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ontent Courtesy: wikipedia, Somnath(dot)org, Shaivam(dot)org, ramnad(dot)tn(dot)nic(dot)in, maharastratourism(dot)gov(dot)in, mahashivratri(dot)org, ujjain(dot)nic(dot)in, srisailam(dot)org, vanamaliashram(dot)org, templenet(dot)com, indiaplaces(dot)com, bhagwatgitausa(dot)com