Washington's interior is a region of hard volcanic substructure, in many places scoured by glacial and river action, that is left largely dry by the shield the Cascades form against the Pacific winds; in some areas, as in the southeastern Palouse hills, loess deposits provide a basis for irrigated agriculture.
Washington is bounded by the Pacific Ocean to the west, Oregon to the south (the Columbia River forming most of this border), Idaho to the east and British Columbia, Canada to the north.
Washington is also notable for being home to four of the five longest floating bridges in the world: the Evergreen Point Floating Bridge, Lacey V. Murrow Memorial Bridge and Homer M. Hadley Bridge over Lake Washington, and the Hood Canal Bridge connecting the Olympic and Kitsap Peninsulas.