Ali-Sadr cave is a magnificent cave located in the Hamadan province of Iran, about 100 km north of the city of Hamadan. It is one of the largest and most beautiful water caves in the world, with a complex system of interconnected tunnels and lakes.

The cave was discovered by a group of Iranian and French explorers in the 1960s, and it was opened to the public in 1976. The cave's unique features include underground rivers, lakes, and waterfalls, as well as striking rock formations and stalactites and stalagmites that have been forming for millions of years.

Visitors to Ali-Sadr cave can take a boat tour through the cave's tunnels and lakes, with the water being so clear that the visitors can see the bottom of the lake, which is several meters below. The temperature inside the cave is also quite mild, remaining around 12 to 13 degrees Celsius throughout the year.

Ali-Sadr cave is not only a tourist attraction but also an important geological and ecological site, as well as a significant archaeological site. It has provided a wealth of information about the region's geology and climate, as well as the lives of the people who lived in the area thousands of years ago.