The district is situated in the Western Ghats mountain range and covers an area of 4,358 square kilometers. The district is known for its hilly terrain, dense forests, and scenic beauty.

Some of the major geographical features of Idukki include: 

Mountains: Idukki is home to some of the highest peaks in South India, including Anamudi (2,695 meters), which is the highest peak in the Western Ghats. 

Rivers: The Periyar, Thodupuzhayar, and Thalayar are the major rivers that flow through the district. 

Dams: Idukki has three major dams, namely the Idukki Arch Dam, the Cheruthoni Dam, and the Kulamavu Dam, which provide electricity and water to the surrounding areas. 

National Parks: Idukki is home to two national parks, namely the Eravikulam National Park and the Pampadum Shola National Park, which are home to a variety of wildlife, including the endangered Nilgiri Tahr. 

Forests: Idukki has dense forests that are home to a variety of flora and fauna, including teak, rosewood, sandalwood, and bamboo. 

Lakes: The district has many natural and artificial lakes, including the Sita Devi Lake, Anayirangal Dam, and Mattupetty Dam, which are popular tourist destinations.