Kaal Sarp Yog is dosha in kundali is a result of one's past karma. It may also happen if the deceased ancestors are displeased or It may occur if a person has harmed a living being/snake either in the present or the previous life as per Hindu mythology and Astrology.
As per astrology when all the planets (Graha) comes between Rahu and Ketu, then signs of Kaal Sarp Yog as regular health problems/Career issues/family issues/delay in work/loss of mental peace is seen in person.
About the location:
Trimbakeshwar Shiva Temple is an ancient Hindu temple in the town of Trimbak,it is is one of the twelve Jyotirlingas, The origin of the sacred Godavari river is near Trimbak.The temple is located between three hills namely Brahmagiri, Nilagiri and Kalagiri. The temple has three lingams representing Lord Brahma, Lord Vishnu and Lord Shiva (Tridev).