San Francisco vs Washington DC

San Francisco packs world-famous sights into a compact, hilly peninsula wrapped in fog and bay views. Ride a clanging cable car up Nob Hill, then drop toward the water for sourdough bread bowls of clam chowder at Fisherman's Wharf. Book Alcatraz well ahead, because the ferry to the former prison island and its gripping audio tour sell out weeks in advance. Walk or bike across the Golden Gate Bridge, coast downhill into Sausalito for seafood by the bay and ride the ferry home past the skyline. Give a full day to wine country, sipping Cabernet in Napa Valley or Pinot Noir in laid-back Sonoma, and save a morning for the towering coast redwoods of Muir Woods, where parking or shuttle reservations are required, or swap in the cliffs and beaches of Half Moon Bay. The city itself rewards slow wandering: dim sum in Chinatown, espresso in North Beach, murals in the Mission and sunset at Ocean Beach. Pack layers whatever the month, since summer fog can drop temperatures into the 50s while the sun shines a few miles inland, and wear comfortable shoes for the steep hills. September and October usually bring the warmest, clearest days of the year.

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.