Idukki Dam

The Idukki Dam is a double curvature arch dam constructed across the Periyar River in a narrow gorge between two granite hills Kuravan and Kuravathi in Kerala, India. At 167.68 metres, it is one of the highest arch dams in Asia. It was constructed and is owned by the Kerala State Electricity Board. It supports a 780 MW hydroelectric power station in Moolamattom, which started generating power on 4 October 1975. Technically, the dam type is a concrete, double curvature parabolic, thin arc dam.
This dam was constructed along with two other dams at Cheruthoni and Kulamavu. Together, the three dams have created an artificial lake that is 60 km² in area. The stored water is used to produce electricity at the Moolamattom Power house, which is located inside nearby rocky caves. The Government of Canada aided in the building of the dam with long term loans and grants.

Features
Idukki Dam is 554 feet tall, constructed between the two mountains – Kuravanmala (839 meters) and Kuravathimala (925 meters ). This project is situated in Idukki District and its underground power house is located at Moolamattom which is about 43 km from the dam.
Twice in the past, the shutters (of Cheruthoni) had to be opened; during the northeast monsoon (October to December) on both occasions. The first time was in 1981 (when the shutters were repeatedly opened and shut between 29 October and 13 November) and the second time was in 1992 (when they were kept open for 12 days from 12 to 23 October). On both occasions, the water level in the dam touched the brim only when the storage built up during the southwest monsoon (June to September) was augmented by the inflow received immediately afterwards following heavy downpour early in the northeast monsoon.

Tourist destination and attraction
Earlier, there was a blanket ban on public entry in to the dam due to security reasons. Later, it was relaxed opening the dam for public for 10 days during the Onam and the Christmas seasons. The duration has been increased to one month since last year. Cameras and cell phones are not allowed inside the dam area. The entry fee is Rs.20 for adults and Rs.5 for children. The fee for 15-minute boating service for five persons is Rs. 600.
Idukki valley is 121 km away from Kottayam, and is a small hill town surrounded by a spread of beautiful, wooded valleys and meandering streams. Idukki is a well known tourist center in Kerala.
The Idukki Wildlife Sanctuary extends over the Thodupuzha and Udumbanchola taluks of Idukki district, spread over 77 km2 and is about 450 – 748 m above sea level. The Idukki Reservoir formed by three dams – Cheruthoni, Idukki and Kulamavu – extends to 33 km2. One can find Elephants, bisons, sambars, deers, wild dogs, jungle cats, tigers, wild boars etc. and a variety of snakes like cobra, viper, krait and a number of non-poisonous snakes in this sanctuary. The birds of Idukki are Jungle fowl, myna, laughing thrush, black bulbul, peafowl, woodpecker, kingfisher etc.
Source : wikipedia 
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Visiting hours : Earlier, there was a blanket ban on public entry in to the dam due to security reasons. Later, it was relaxed opening the dam for public for 10 days during the Onam and the Christmas seasons. The duration has been increased to one month since last year. Cameras and cell phones are not allowed inside the dam area. The entry fee is Rs.20 for adults and Rs.5 for children. The fee for 15-minute boating service for five persons is Rs. 600.