Cooper Hewitt, Smithsonian Design Museum

The only museum in the United States devoted exclusively to historical and contemporary design, and the deepest design collection a North American visitor can reach without a flight across an ocean: more than 215,000 objects spanning 30 centuries. It lives in the landmark Carnegie Mansion on the Upper East Side, so expect a grand former home rather than white-box galleries. Design Across Time, a long-running installation of 125 works from the collection, fills the first floor and rotates objects over several years, which gives repeat visitors a reason to come back. Add whatever temporary show is on for a satisfying half day.