of Kyoto was formed on April 1, 1889. The construction of Lake Biwa Canal in 1890 was one measure taken to revive the city. The population of the city exceeded one million in 1932. Contemporary history There was some consideration by the United States of targeting Kyoto with an atomic bomb at the end of World War II because of the possibility that the city's importance was great enough that its loss might persuade Japan to surrender. In the end, at the insistence of Henry L. Stimson, Secretary of War in the Roosevelt and Truman administrations, the city was removed from the list of targets and replaced by Nagasaki. The city was largely spared from conventional bombing as well, although small-scale air raids did result in casualties. During the occupation, the U.S. Sixth Army and I Corps were headquartered in Kyoto. As a result, Kyoto is one of the few Japanese cities that still have an abundance of prewar buildings, such as the traditional townhouses known as machiya. However, modernization is continually breaking down traditional Kyoto in favor of newer architecture, such as the Kyōto Station complex. Kyoto became a city designated by government ordinance on September 1, 1956. In 1997, Kyoto hosted the conference that resulted in the protocol on greenhouse gas emissions (United Nations Framework Convention on Climate Change). Geography Terrain Kyoto is located in a valley, part of the Yamashiro (or Kyoto) Basin, in the eastern part of the mountainous region known as the Tamba highlands. The Yamashiro Basin is surrounded on three sides by mountains known as Higashiyama, Kitayama and Nishiyama, with a maximum height of approximately above sea level. This interior positioning results in hot summers and cold winters. There are three rivers in the basin, the Uji River to the south, the Katsura River to the west, and the Kamo River to the east. Kyoto City takes up 17.9% of the land in Kyoto Prefecture and has a total area of . Kyoto sits atop a large natural water table that provides the city with ample freshwater wells. Due to large-scale urbanization, the amount of rain draining into the table is dwindling and wells across the area are drying at an increasing rate. Climate Kyoto has a humid subtropical climate (Köppen Cfa), featuring a marked seasonal variation in temperature and precipitation. Summers are hot and humid, but winters are relatively cold with occasional snowfall.