Cave of Darkness
From Dragon Ball Encyclopedia, the ''Dragon Ball'' wiki
The Cave of Darkness is a very dark cave located in the Ice Maze.
The Ultra Divine Water was kept and guarded by Darkness, a mysterious entity who lived inside the Cave of Darkness. The cave was sacred and kept from those not worthy of drinking the water. Son Goku and Yajirobe both entered the cave and faced multiple obstacles and challenges once inside, but eventually made it to the Ultra Divine Water.
Goku drank the water and suffered a great deal from it. Once he recovered, however, the water awakened the necessary sleeping powers within him to defeat the evil Piccolo Daimao.