地ち底てい湖こ

noun

underground lake; subterranean lake

A lake located beneath the earth's surface, often in caves or deep geological formations.

• その洞どう窟くつの奥おくには美うつくしい地ち底てい湖こが広ひろがっていた。

  A beautiful underground lake spread out deep inside the cave.

• 地ち底てい湖この水みずは驚おどろくほど澄すんでいた。

  The water of the subterranean lake was surprisingly clear.