Approaching Hoover Dam from the Nevada side, in the eight miles from Boulder City you pass a Nevada Welcome Center, a National Park Service visitors center for Lake Mead National Recreation Area, and a peculiar parade of electrical generators, transformers, and capacitors all secured by cyclone fencing topped by razor wire and barbs to keep out intruders.

  Next up is the parking lot for the visitors center (daily; $10, plus $5 parking; 702/294-3517), which finally opened in 1995, 10 years behind schedule and $100 million over budget. The steep admission price buys you a half-hour film, a self-guided museum tour, and an elevator ride down inside the dam to gape at the humming turbines, which at peak times generate some 2000 megawatts of electricity, enough to supply a million homes and still have enough juice left over to light up the Las Vegas Strip. Beyond the visitors center, US-93 rolls right over the top of the gargantuan wedge of Hoover Dam: nearly a quarter-mile across, 726 feet high, 660 feet thick at the base, all accomplished with a mere seven million tons (that’s 14 billion pounds) of concrete. If you just want to see the dam, you can walk across it for free and peer down at the lake or distant river below; because of security concerns, pedestrians are banned after dark.

  Upstream from the dam spreads Lake Mead, the largest man-made lake in the western hemisphere. Containing roughly 30 million acre-feet or just over nine trillion gallons, Lake Mead irrigates some 2.5 million acres of land in the United States and Mexico, while helping to control the river’s seasonal flooding. The lake is a very popular recreation site, with thousands of water-skiers and others flocking to its 500 miles of shoreline year-round.