Kallanai (also known as the Grand Anicut , Tamil : கல்லணை) is an ancient dam, which is built (in running water) across the Kaveri river in Tiruchirappalli District in the state of Tamil Nadu in India.[1] Located at a distance of 15 km from Tiruchirappalli, the dam was originally constructed by the Chola king Karikalan in 2nd century AD. It is located on Kaveri river approximately 20 KM from Trichy, but the dam falls under Thanjavur district .