Washington Monument

The 169 m marble obelisk honouring the first president marks the centre of the capital and is the tallest structure in Washington. Construction began in 1848, stalled for decades for lack of money, and was completed in 1885; the colour change about a third of the way up shows where work resumed with stone from a different quarry. It was the tallest structure in the world until the Eiffel Tower in 1889 and remains the tallest obelisk and the tallest predominantly stone structure anywhere. The walls are 4.6 m thick at the base.

An elevator takes visitors to eight small viewing windows at the top, with the best overview of the Mall, the White House and the Potomac. About 670,000 people ride up each year. A 2011 earthquake caused 150 cracks and a three-year, 15 million dollar repair. Fifty US flags circle the base.

Practical: Free, but timed tickets are required for the elevator and sell out quickly online; a limited number are released each morning. The exterior and the surrounding lawn are open at all times and are the classic photo spot with the Capitol or the Lincoln Memorial in the background.