What is "cheonggyecheon"

Cheonggyecheon ( Hangul: 청계천) is a 10.9 km (7.0 miles) long, modern public recreation space in downtown Seoul, South Korea. The massive urban renewal project is on the site of a stream that flowed before the rapid post-war economic development caused it to be covered by transportation infrastructure. The $900 million project initially attracted much public criticism but, after opening in 2005, has become popular among residents and tourists.