Hangzhou is known for its historic relics and natural environment. Although Hangzhou has been through many recent urban developments, it still retains its historical and cultural heritage. Today, tourism remains an important factor for Hangzhou's economy. One of Hangzhou's most popular sights is West Lake, a UNESCO World Heritage Site. The West Lake Cultural Landscape covers an area of and includes some of Hangzhou's most notable historic and scenic places. Adjacent to the lake is an area which includes historical pagodas, cultural sites, as well as the natural environment of the lake and hills, including Phoenix Mountain. There are two causeways across the lake.