Las Vegas vs Washington DC

Las Vegas built an entire city around entertainment — the Strip's casino resorts recreate Paris, Venice, and New York within walking distance of each other, staging residencies, fountain shows, and round-the-clock dining. Beyond the neon, Red Rock Canyon and the Grand Canyon are both feasible day trips from a city that never fully turns its lights off.

Washington DC may be the best family city in America, mostly because so much of it is free. In three days with kids you can stand under real spacecraft at the National Air and Space Museum, meet the Hope Diamond and towering dinosaur skeletons at the National Museum of Natural History, and see the original Star-Spangled Banner at the National Museum of American History, all without paying admission. Some sites use free timed-entry passes, so reserve them before you go. Between museums, let kids run on the grassy National Mall, ride the carousel and picnic with food-truck lunches. Save an evening for the monuments at sunset, when the Lincoln Memorial glows, the Reflecting Pool mirrors the Washington Monument and the crowds thin out. The Metro makes getting around easy, and younger children ride free with a paying adult. With more time, see giant pandas, elephants and great apes at the free National Zoo, tour the US Capitol and the stunning Library of Congress, crack codes at the International Spy Museum, and day-trip to George Washington's Mount Vernon and the brick sidewalks of Old Town Alexandria. Spring and fall are ideal, with cherry blossoms in late March to early April.