What's a good 3-day itinerary for Washington DC?

Three days in Washington DC, three zones, no backtracking. Day 1 is the National Mall from west to east on foot. The Lincoln Memorial at 7:30am feels different than at noon, dedicated in 1922 and still cool inside the marble colonnade before the August heat sets in. Five minutes northeast sits the Vietnam Veterans Memorial. By 9am, reach the World War II Memorial and its 56 granite pillars. The Washington Monument, started in 1848, opens timed tickets at 9:30am. Book these free tickets on recreation.gov at least 2 days ahead or you will not get in. The elevator to the 500-foot observation deck takes 70 seconds. By 11am, cross east to the National Gallery of Art, founded 1937, where the west building's Vermeer and Raphael rooms tend to be quieter than the modern east wing. Lunch at the Gallery's Garden Cafe by 12:30pm. Walk past the White House north fence at 3pm for the exterior view. Interior tours require a congressional request filed 3 weeks ahead. End at Old Ebbitt Grill on 15th Street NW by 5pm for oysters and a cold draft. The place has served since 1856. About 11 kilometres.

Day 2 shifts 3 kilometres east to Capitol Hill. The U.S. Capitol Visitor Center opens at 8:30am for the free 45-minute guided tour. Book at least 48 hours ahead online. The rotunda's painted ceiling catches quiet morning light in the first slot, and the Brumidi corridors smell faintly of old plaster. Walk across 1st Street to the Library of Congress Jefferson Building by 10:30am. It holds 173 million items. The Great Hall's stained glass and gilded arches are worth 30 minutes. Lunch at Ted's Bulletin on 8th Street SE by noon. Their homemade Pop-Tarts cost around $6 each and taste nothing like the boxed version. Eastern Market, 2 blocks south on 7th Street SE, runs a weekend flea market outside and a Tuesday-through-Sunday food hall inside. Mind you, the best produce vendors clear out by early afternoon. By 2pm, take the Circulator bus back west to the National Museum of Natural History, founded 1910, for the Hope Diamond and the Ocean Hall's life-size whale model. Every Smithsonian museum is free. For dinner, walk north to Zaytinya on 9th Street NW in Penn Quarter, where eastern Mediterranean small plates run $14-$18 each. About 9 kilometres with the bus.

Day 3 leaves the federal core of Washington DC. Take a rideshare or the DC Circulator to M Street NW in Georgetown by 9:30am. Start at Baked and Wired on Thomas Jefferson Street for coffee and a quiche. The shop seats maybe 15 people, and the line might reach the sidewalk by 10am, but it moves in about 8 minutes. Walk the C&O Canal towpath 20 minutes north along the stone-walled channel where mule-drawn barges hauled coal in the 1830s. The air runs cooler down by the water, and you'll hear runners and the occasional kayaker on the Potomac. Martin's Tavern on Wisconsin Avenue serves lunch in the same booth where JFK reportedly proposed to Jackie in 1953. The crab cake sandwich runs about $24. After lunch, rideshare 15 minutes north to the Washington National Cathedral, construction started in 1910 and not finished until 1990. Look for the Darth Vader grotesque on the northwest tower, roughly 60 feet up. You will need binoculars. End the evening on 14th Street NW at Le Diplomate for French brasserie food. The steak frites is $39, and the sidewalk patio fills by 7pm. About 8 kilometres with transit.

Mid-August mornings in Washington DC currently start around 21°C with 77% humidity, but afternoons likely reach 32°C or higher. Carry water and plan indoor museum time between 1pm and 3pm when the heat peaks. Metro opens at 5am on weekdays. A SmarTrip card runs $2 to $6 per Metro ride depending on distance and time of day. Worth noting, most Mall museums close at 5:30pm. The 3-day total comes to about 28 kilometres of walking plus short transit segments. If you have only 2 days, drop Day 3. Georgetown is pleasant, but the Mall and Capitol Hill are why people fly to Washington DC.