dark tunnel to lake proval, pyatigorsk, stavropol krai, russia. people look at water in cave, tourist attraction of pyatigorsk.

pyatigorsk russia proval people stavropol cave dark lake tunnel water travel entrance resort building landmark architecture attraction caucasian caucasus city destination door failure front grotto historical karst kavkaz krai mineral monument mountain nature opening outdoor place russian scenery sightseeing sinkhole stone summer tourism tourist town underground vacation wall background