Rishi Vashisht was one of the seven great sages (Saptarishi) of ancient India.
He was the son of Lord Brahma and the teacher of Lord Rama.
This gufa or cave is located few distance from the city of Rishikesh.
The cave is famous for meditation used by Rishi Vashisth and his wife during his time. You may meditate here and there are timings for entrance. Do check the timing before going to the cave.