Kallanai (also known as the Grand Anicut) is an ancient dam built by Karikala of Chola dynasty in 150 CE. It is built (in running water) across the Kaveri river flowing from Tiruchirapalli District to Thanjavur district, Tamil Nadu, India. The dam located in Thanjavur district. Located at a distance of 15 km from Tiruchirapalli, 45 km from Tanjavur. 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. History The dam was originally built by King Karikalan of the Chola Dynasty in c. 100  – c. 150 CE. It is located on the river in Thanjavur district, exactly 14 km from the city of Tiruchirappalli and 45 km from the city of Thanjavur. The idea behind the construction of the dam was to divert the river to the delta districts thereby boosting irrigation. This dam was re-modeled by the British during the 19th century. In 1804, Captain Caldwell, a military engineer, was appointed...