This is a consecrated linga of Shree Shool Tankeshwar Mahadev.
There is a place to sit and meditate. You can go into meditative states here effortlessly.
How to Get there
The temple is located in Madhopur. There is another temple in Dasashwamedh Ghat in Varanasi.
Map:
https://goo.gl/maps/55pXonZ52Lh2xmRD7
About Shree Shool Tankeshwar Mahadev
When river Ganga approached Kashi with a violent force, Lord Shiva threw his Trishul (Trident) hard into the ground, just before the entry point to the South of Kashi. By this action,
Ganga had to slow down her force and she agreed to flow gently through Kashi and that she would always remain in Kashi, giving happiness to the residents thereat. Scientifically speaking, the River Ganga is perennial in Kashi and at some points, even during the dry summer, the depth is over 130 feet. Accordingly, people believe that Shool Tankeshwar temple is at a point almost 2 Kms. South of Assi.
But according to Kashi Khand, the place has been mentioned in the vicinity of Prayag Teerth, which is almost a part of Dasaswamedh.