Shivlinga (Lingam)
Shri Shiva, the supreme god of hinduism, represents the spirit of the universe or we can say using christian terminology, God the Father.
Shiva is in point of fact formless, He never incarnated. According to the legend, Shri Shiva took the form of a stone when Shri Vishnu and Shri Brahma wanted to worhip him. They asked Shri Shiva to take any form because they found it very hard to worship formless god. And Shri Shiva took a form of a lingam. Some sources affirm that lingam is a projection of Shri Shiva's heart. In legend about demon Ravana it is said that Shri Shiva took a lingam from His heart.
Ignorant people refer Lingam to some sexual meanings, but it doesn't correspond to hindu scriptures. It is a form of heretic teaching which was popular in India in 15th century.
Shivling mountain (on photo) is near [Goumukh] cave, from which the sacred river Ganga flows. Its height s 6543 meters.
You can see this mountain in 5 km before [Gangotri], than it dissapears and reappears only in 5 km before Goumukh.