Kallanai (also known as the Grand Anicut) is an ancient dam. It is built (in running water) across the Kaveri river flowing from Tiruchirapalli District to Thanjavur district,Tamil Nadu, India.
The dam located in Trichy district.Located at a distance of 15 km from Tiruchirapalli, 45 km from Tanjavur, the dam was originally constructed during the reign of Chola king Karikalan in c.150 AD.It is the fourth oldest water diversion or water-regulator structures in the world and the oldest in India that is still in use.Because of its spectacular architecture, it is one of the prime tourist spots in Tamil Nadu.