Combining a visit here with a drive through Valley of Fire State Park makes for a worthwhile full-day trip out of Vegas. Construction on the dam - which contains enough concrete to pave a highway across the continental United States - began in 1931 and, upon its completion, it was hailed as the Eighth Wonder of the World. At the top, there's a self-paced tour providing presentations at six different points. Visitors can stroll past the enormous power plant generators, photograph the bronze Winged Figures of the Republic sculptures, browse through an exhibit gallery, and walk out on an observation deck with a panoramic view of Lake Mead and the Colorado River. As a result of heightened security instituted after 9/11, all vehicles crossing the structure from Nevada into Arizona are subject to search.