Casa Botines is a Neo-Gothic mansion designed by Antoni Gaudí in 1892, one of only three buildings he completed outside Catalonia. It sits on the Plaza de Santo Domingo, directly opposite a much more conventional building — the contrast makes Gaudí's instincts clear even at a glance.
The building now houses a Gaudí museum on the ground floor, with interactive exhibits on the house's history and Gaudí's methods. The upper floors display changing exhibitions. Worth a visit even if you've seen Gaudí's Barcelona work — this is a different, more restrained register.