Nanda Devi

Declared in 1982 and a UNESCO World Heritage Site since 1988, Nanda Devi National Park surrounds India's second highest mountain (7,816 m) and was closed entirely to mountaineering and tourism in 1983, after it emerged that a nuclear surveillance device — placed secretly in the 1960s by a joint operation between the American CIA and Indian intelligence to monitor Chinese nuclear tests — had been lost on the mountain during an expedition, raising fears of radioactive contamination that led the authorities to restrict access as a precaution for years.