La Pedrera of Barcelona
La Pedrera , a Gaudí masterpiece, was built between 1905 and 1910 as a combined apartment and office block. Formerly called the Casa Milà, it's better known now as La Pedrera (the Quarry) due to its uneven grey stone facade that ripples around a street corner - it creates a wave effect that's further emphasized by elaborate wrought-iron balconies.
Visitors can tour the building and go up to the roof, where giant multicoloured chimney pots jut up like medieval knights. On summer weekend nights, the roof is eerily lit and open for spectacular views of the city. One floor below the roof is a modest museum dedicated to Gaudí's work.