This is the world's second and Asia's first arch dam 555 ft in height and 650 ft. in width, proudly standing between the two mountains - 'Kuravanmala' (839 meters) and 'Kurathimala' (925 meters ). A prestigious project of our nation, its underground power house is located at Moolamattom, about 19 kms from Thodupuzha. Idukki Dam is 43 kms away from Moolamattom. The Idukki reservoir is formed by three dams (Idukki, Cheruthoni and Kulamavu) and natural hills.

The possibility of Hydroelectric development at Idukki was first conceived in 1919. History has it that Shri Kolumban, the head of the 'Araya' race in1922, showed the Malankara Estate Superintendent and his friend Thomas, who were on hunting spree in the forest, the spot of the present Arch Dam. He told them of the legend of Kuravan and Kurathi Hills. Thomas was stirred by the sight of water flow between the mountains and it is his idea that has made the dream of Idukki Arch Dam a reality.. Sri. W.J.John of Malankara Estate submitted a report to the Government of Travancore in 1932 on the possibility of constructing a dam at Idukki for power generation purposes.

The project was posed for Canadian aid, its scope was enlarged and a revised project report was drawn up in 1956-66. The construction of this dam commenced on 30 April 1969. Storage of water in Idukki reservoir commenced in February 1973. . The trial run of the first machine was on October 4, 1975. The commercial operation of the power station was commissioned by the then Prime Minister Smt. Indira Gandhi, on February 12, 1976.

Construction of this arch dam and two other dams at Cheruthony and Kulamavu has created an artificial lake of 60 sq. km. width and the water stored is utilised for production of electricity at the unique Moolamattom power house, located inside rocky caves. Best season to visit the dam is from August to March.