Hoover Dam sits 30 miles southeast of Las Vegas on the Nevada–Arizona border and is one of the great engineering achievements of the 20th century. Built during the Depression between 1931 and 1936, the 221-metre concrete arch-gravity dam holds back Lake Mead, the largest reservoir in the United States by volume. The scale is hard to take in until you are standing on it: the spillways alone could swallow a battleship.
You can walk across the dam for free and feel the drop from the pedestrian walkways. The ticketed Powerplant Tour takes you inside to the cathedral-like generator hall, where turbines still produce electricity for Nevada, Arizona, and California, and the longer Tunnel Tour goes deeper into the original construction galleries — worth it for anyone curious about how the thing was actually built. The nearby Mike O'Callaghan–Pat Tillman Memorial Bridge gives the best view of the dam from above; walk out to the centre for the full panorama.
Lake Mead spreads behind the dam across the Mojave Desert and is the heart of a national recreation area. Boulder Beach, the closest swimming and launch point, offers kayaking, paddleboarding, and boat rentals, and the lake's countless coves draw houseboaters for days at a time. Drought has dropped the water dramatically over the past two decades, leaving a pale "bathtub ring" high on the canyon walls that is sobering to see in person — a clear marker of how much the reservoir has shrunk.
Drive yourself from Las Vegas in about 35 minutes, or join one of the many half-day tours that run from the Strip if you are without a car. Combine the visit with the dam-workers' town of Boulder City just up the hill for an easy full day out.