What do the three places in the passage have in common?

Not all of India's World Heritage Sites were built by people. Some are natural places, protected for their wildlife and landscapes. Three of the best known were listed in the 1980s.

Kaziranga National Park, in the heart of Assam, became a World Heritage Site in 1985. It is one of the last areas in eastern India left undisturbed by people. It is home to the world's largest population of one-horned rhinoceroses, as well as tigers, elephants, panthers, bears and thousands of birds.

Keoladeo National Park, in Rajasthan, was listed in the same year. It was once a duck-hunting reserve of the Maharajas. Today it is one of the major winter homes for large numbers of water birds that fly in from Afghanistan, Turkmenistan, China and Siberia. Some 364 kinds of birds have been recorded there, among them the rare Siberian crane.

The Sundarbans National Park followed in 1987. The Sundarbans, in the delta of the Ganga, cover about 10,000 square kilometres of land and water, a little more than half of it in India and the rest in Bangladesh. They contain the largest area of mangrove forest in the world, and they shelter many rare or endangered species, including tigers, water mammals, birds and reptiles.