Smithsonian Institution, Washington DC

 The Smithsonian is the world’s largest research and museum complex, with 19 museums and galleries, the National Zoological Park, and various research stations. More than 137 million objects detailing America’s story are housed here, so you’d better prepare for a long week of walking. There’s so much to see that, if you spent one minute day and night looking at each object on exhibit, in ten years you’d see only ten percent of the whole.