Ali Sadr or Alisadr Cave is a cave located in 75 km north of Hamedan in Iran. It was formed 130-190 million years ago in the second Jurassic period. The caves walls can extend up to 40 meters high, and it contains several large, deep lakes.
It has a river flowing through it and and so traveling through the cave is mostly done by boats. In the summer of 2001, a German/British expedition surveyed the cave to be 11 kilometers long. The main chamber of the cave is 100 meters by 50 meters and 40 meters high.
Ali Sadr cave is situated between the large cities in Hamedan, Tehran and Zanjan making it a popular destination for Iranians and foreign tourists.
The cave was originally discovered during the reign of Darius I (521-485 BC) which can be verified by an old inscription at the entrance of the tunnel. However, the knowledge of the existence of the tunnel was lost, and only rediscovered in 1978 when a local shepherd followed the tunnel searching for water or a lost goat.