The museum at National Geographic Society headquarters can’t compete with the Smithsonian’s more extensive offerings, but it can be worth a stop, depending on what’s showing. Exhibits are drawn from the society’s well-documented expeditions to the far corners of the Earth, and they change every three months or so. In spring and fall, the onsite theater shows free documentary films on Tuesdays at noon.

The society also hosts concerts and lectures by famed researchers and explorers; most programs have a fee.