Jiangsu has a long history of a relatively developed economy and culture. Rich in landscape gardens, scenic attractions and historical sites, it is noted for having the largest number of historical cities in the country. Such cities include Nanjing, Suzhou, Yangzhou, Zhenjiang, Changshu, Xuzhou and Huai'an. There are 20 scenic spots, 23 forest parks, 6 holiday resorts and 416 cultural heritage sites under the state and provincial-level protection. Classical gardens in Suzhou were put on the world cultural heritage site list by the United Nations Educational, Scientific and Cultural Organization.