Many ancient Shiva Temples could be witnessed in Kashi. one of them is the Bhoor Bhuva Suva Ling Temple. The importance of this Temple is mentioned in Kashi Khand.
Legend
Rudra Vasam is the name of the location where Lord Shiva donned the skin of Gajasur after killing him, according to Kashi Khand, Chapter 69. (One can refer to Krithi Vaseshwar.)
When Nandi offered his prayers and mentioned that this sacred area had 68 places of devotion for Lord Shiva, the Lord, then known as Krithi Vaseshwar, was seated with Goddess Uma Devi.
Nandi placed several idols/Shiv Lings at Kashi after bringing them from various other locations. One Shiv Ling by the name of Bhoor Bhuva Suva Ling has emerged by itself in Kashi from the Gandamadan Mountains. Worshiping this Ling would make devotees very joyful throughout heaven.