Michael Heizer has spent 50 years completing 'City,' and now he's opening it to the public, by reservation only. Photo by Elliott Cowand Jr / Shutterstock.com

A concrete walkway with a ramp in the distance. A giant boulder, probably at least 10 feet by 10 feet, is suspended above the walkway. This photo was taken at the Los Angeles County Museum of Art. Photo by Elliott Cowand Jr / Shutterstock.com