The entire Summer Palace is centered around Longevity Hill and Kunming Lake, with the latter covering about three quarters of the area. Most of the important buildings were built along the north–south axis of Longevity Hill, which is divided into the front hill and the back hill. There are three small islands within Kunming Lake: Nanhu Island, Zaojiantang Island and Zhijingge Island. The West Dam of Kunming Lake divides the lake into two. The East Dam was constructed during the reign of the Guangxu Emperor. The attractions in the Summer Palace may be divided into six different sections or scenic areas: the Halls, Longevity Hill, Kunming Lake, the Farming and Weaving Picture Scenic Area, the Long Corridor, and the Central Axis area. Summer Palace is among the most-visited destinations in China, ranking in the top five, and attracts about 10 million tourists annually.