Wikipedia
Nakhcheer
Nakhcheer or Chal-Nakhjir is a cave situated in Markazi Province of Iran. It is a limestone cave approximately 70 million years old. Parts of the cave including its internal lake have been prepared for easy tourist access. It was discovered in 1989 and registered as a national monument in 2001. Its interior is made of crystals, dolomite sediments, stalactites and stalagmites.