Gaudi's Cathedral

Temple Expiatori de la Sagrada Familia (Temple of the Sacred Family) was unfinished at the time of Gaudí's death in 1926 and it's still far from complete. It's striking and surreal.

The cathedral has been added to by other architects, but none of them have had the vision (or the craziness) of Gaudi - a weird dude if ever there was one.