Mythology about Somnath Temple:
Ancient Indian traditions maintain a close relationship of Somnath with release of Chandra (Moon God) from the curse of his father-in-law Daksha Prajapati. Moon was married to Twenty-Seven daughters of Daksha. However, he favoured Rohini and neglected other queens. This angered their father Daksha. He cursed Chandra to decrease in size every day. With the advice of Prajapita Brahma, Moon arrived at the Prabhas Teerth and worshipped Bhagvan Shiva. Pleased with the great penance and devotion of Moon, Bhagvan Shiva blessed him and relieved him from the curse of darkness and gave him a boon.

Img Src: Internet

Img Src: Internet
The boon was that Lord Shiva would place Chandra on His head.
In the Shiva Purana and Nandi Upapurana, Shiva said, `I am always present everywhere but specially in 12 forms and places as the Jyotirlingas`. Somnath is one of these 12 holy places. This is the first among the twelve holy Shiva Jyotirlings.
Another story states that Soma, the Moon god (Chandradeva), is believed to have lost his lustre due to a curse, and he bathed in the Sarasvati River at this site to regain it. The result is said to be the waxing and waning of the moon. The name of the town, Prabhas, meaning lustre, as well as the alternative names Someshvar and Somnath (“the lord of the moon” or “the moon god”), arise from this tradition.
History of Somnath Temple

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Reconstructed several times in the past after repeated destruction by several Muslim invaders and rulers, it is unclear when the first version of the Somnath temple was built. It is estimated to be built between the early centuries of the 1st-millennium to about the 9th-century CE. It is also called “The Shrine Eternal” because the temple was looted and destroyed several times in the past. However, it was gloriously rebuilt every single time after that.
The modern temple was reconstructed with the resolve of Sardar Patel who visited the ruins of Somnath temple on November 13 1947. Then President of India, Dr. Rajendra Prasad, did the Pran-Pratistha at the existing temple on 11 May 1951.
The structure of the Somnath Temple

The temple is has three main areas – the Garbhagraha, the Sabhamandapam, and the Nrityamandapam. The Shikhar of the temple is 150 feet high. The Kalasam or the Kalash weighs 10 tonnes. The flag pole at the top is 8.2 meters long. The temple reflects the skills of the Sompura Salats, Gujarat’s famed stonemasons.
Some of the festivals celebrated at Somnath Temple are:

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Shravan Month: Shravan Maas falls on the fifth month of the Hindu calendar, starting late July and ending by the third week of August.
Mahashivratri: On this day Lord Shiva married Goddess Parvati. This festival usually occurs in late February to early March. This year Shivratri will be celebrated on Tue, Mar 1, 2022.
Golokdham Utsav: It signifies the birth of Lord Krishna, more popularly known as Janmashtami. It occurs mostly in the month
Kartik Purnima Fair: The fair lasts for five days. It iscelebrated on the Purnima (full moon) day or the fifteenth lunar day of Kartik (November–December).
Somnath Sthapana Divas: The foundation day which is celebrated on the 11th of May.