Guided tour at the Tate Modern
You’ve probably already got this modern art gallery on your London bucket list (after all, it costs nothing), but make the most of it by catching one of four complimentary daily tours. That way, you can also learn the difference between a Turner, a Pollock, and what’s just a used Kleenex on the floor.
Museo Nacional del Prado
For a taste of classic art, check out Spain’s main national art museum during the evening when there’s no entry fee. Here you can find one of the finest collections of European art, including paintings and sculptures from as far back as the 12th century.