On a budget, Royal Palace of Madrid still earns its price.
€14 (free last 2 hours for EU citizens, Mon–Thu)
The gilded staterooms, throne room and Tiepolo ceilings are genuinely opulent, and the exterior plaza is one of Madrid's grand sights. The catch: the timed-ticket lines get long, photography is restricted indoors, and on state-event days rooms close without much warning.