America's Top Free Attractions
David Coleman / Alamy
The National Zoo, National Museum of Natural History, and National Air and Space Museum—which displays The Spirit of St. Louis—are the biggest crowd-pleasers among the 18 Smithsonian institutions in D.C., otherwise one of the country’s priciest cities. Indeed, making knowledge accessible is key to the mission of the world’s largest museum and research complex. Affordable-travel expert Tim Leffel observed that the three museums he visited with his wife and daughter would have set them back more than $100 in most European capitals. And here's a bonus: you can download a free app about the National Mall sites from the National Park Service.