Built during the Great Depression as a way to provide jobs, Hoover Dam is a marvel of modern engineering. The 726-foot-high dam contains Lake Mead, the largest reservoir in the United States, and provides hydroelectric power to much of Nevada, Arizona, and California.
Built on the Nevada and Arizona state line, the dam is just a 45-minute drive from the center of Las Vegas, or a short helicopter flight. You can walk out onto the dam for vertigo inducing views over the edge, or look out over Lake Mead. Tours of the Hoover Dam Power Plant are also available; note that some tours can only be purchased at the dam itself.
Official site: http://www.usbr.gov/lc/hooverdam/
Accommodation: Where to Stay near the Hoover Dam