Grand Coulee Dam, part of the Columbia Basin Project, located on the Columbia River in Washington State, is one of the largest concrete structures in the world. The dam is also the largest hydropower producer in the United States with a total generating capacity of 6,809 megawatts. The visitor center is open daily 9 a.m. to 5 p.m., except for Thanksgiving, December 25, and January 1. From Memorial Day through September 30 the visitor center is open from 8:30 a.m. until the end of the laser light show each evening. Free guided tours are available from 10 a.m. to 5 p.m.