Ali Sadr Cave is a cave located about 100 kilometers north of Hamedan in western Iran .The cave walls can extend up to 40 meters high, and it contains several large, deep lakes.
The cave has a river flowing through it and most travel through the cave system is done with a boat. Ali Sadr cave is situated between the large cities in Hamadan, Tehran and Qom making it a popular destination for Iranians. The cave was originally discovered during the reign of Darius I (485 BC) which can be verified by an old inscription at the entrance of the tunnel. This is the only cave open to tourism in Iran and according to IRNA it attracts 300,000 visitors per year. A German/British expedition of the cave took place in 2001.