Hoover Dam is one of America’s greatest engineering marvels, built in the 1930s by over 21,000 workers using materials sourced from every U.S. state. Standing 726 feet tall and 660 feet thick at its base, the dam holds back immense water pressure and contains enough concrete to wrap a sidewalk around the Earth. From the decks of the Desert Princess on Lake Mead, you'll enjoy unbeatable views of this National Historic Landmark—visited by over seven million people a year and celebrated for its scale, history, and hydroelectric power.