Hoover Dam on the Colorado River, is a feature of the Boulder Canyon Project. Located on the Arizona-Nevada state line, at 726 feet it is the highest concrete dam in the United States, a National Historic Landmark, and one of America's Seven Modern Civil Engineering Wonders. The Bureau of Reclamation started conducting guided tours through Hoover Dam and Powerplant in 1937. More than 1,000,000 visitors a year take the tours and millions more drive across the dam. A visitor center and 400 car parking garage opened in 1995. The visitor center includes a theater, exhibit gallery, and a rooftop observation deck. Food and beverages are available at the dam also. Visitors may visit an outdoor overlook above the dam and a room where power is generated. The visitor center contains an exhibit gallery and a film about the dam's construction. Operating Hours: Open 9:00 AM -- Close 5:00 PM. (All times are for the Pacific-time zone). The Hoover Dam Visitor Center is open every day of the year except for Thanksgiving and Christmas. Note: Pedestrians are prohibited from the top of the dam during hours of darkness. Please click on the Hoover Dam web page to learn more about visitor opportunities.