Built at a cost of $49 million — or $821 million with inflation — the Hoover Dam stops the Colorado River to create Lake Mead, itself a popular attraction. It has been open to visitors since 1937, and today, roughly 1 million people visit annually; the busy season falls between Memorial Day and Labor Day. Located roughly 35 miles east of Las Vegas, the Hoover Dam is an easy — and worthwhile — day trip from Sin City. A number of tour groups offer sightseeing excursions from Vegas hotels for those travelers who don’t have access to a vehicle.