Palacio Real de Madrid

Europe's largest royal palace by floor area — 3,418 rooms, though only around 50 are open to the public, dripping with frescoes, Stradivarius violins, and a Throne Room that still hosts state ceremonies. The Spanish royal family no longer lives here, which is exactly why you can walk through it.

Book a timed slot online to skip the queue that forms daily along Calle de Bailén — walk-up tickets sell out fast in high season. The Changing of the Guard happens on the forecourt every Wednesday and Saturday at 11:00 (October–June) and is free to watch from outside the ticketed area. Photography isn't allowed inside the state rooms, so the ornate ceilings are one thing you'll have to remember rather than photograph.