Deep underneath the city of Yekaterinburg in Russia lies the most colorful cave you have ever laid your eyes upon. The walls of this abandoned salt mine is covered with psychedelic patterns, caused by the natural layers of carnallite, a mineral used in the production of plant fertilizers, and is most often yellow to white or reddish, but can sometimes be blue or even completely colorless. A small portion of the carnallite mines remain in use, but most of the passageways are now closed and off-limits to the public without a special government permit.

The following pictures were taken by photographer Mikhail Mishainik, 29, who spent over 20 hours exploring the dimly lit labyrinth and has stayed overnight on at least three occasions.

“The mines are huge and stretch many kilometers in width and length, a single tunnel can be over four miles long. It is hard to describe how it feels being so far down, you lose all track of time and the air is very dry, you always feel thirsty,” said Mikhail Mishainik to The Daily Mail.

“There is the possibility of a gas leak from chemicals such as methane, hydrogen sulphide carbon dioxide as well the risk of a landslide,” Mikhail added. “The danger element is part of the fun and it’s a special feeling being somewhere very few people have seen.”