This Feb. 28, 2013 photo shows a U.S. Air Force North American X-15 aircraft hanging inside the Smithsonian Institution Air and Space Museum in Washington. There are probably more free things to do in the U.S. capital than nearly any other major city in the world. The most popular museums and the zoo are free, thanks to government funding, as well as the picturesque memorials and monuments. With so many free options, the biggest challenge might be narrowing down what to see. (AP Photo/Alex Brandon)
