Casa Batlló is an ordinary apartment block that Gaudí turned into stone bone and broken glass. The lower floors are Montjuïc sandstone carved into columns shaped like leg bones, and the cast-iron balconies read as masks. The wall above is clad in trencadís: ceramic and glass fragments, warm near the street, blue at the roofline. A roof of scaled tile with a cross-topped turret finishes it. Barcelona called the result the Casa dels Ossos, the house of bones.
Inside, straight lines are rare. The oak doors curve, the stair rail winds up the well in one unbroken twist, and the plaster of the salon ceiling spirals out from the light fitting at its centre. Climb to the attic above the top floor and the decoration stops altogether: whitewashed catenary arches in a row, like the inside of a ribcage. The block under all of this was an ordinary one, and the textile manufacturer who owned it meant to knock it down. Gaudí talked him into keeping the shell and rebuilding everything else around it. The family lived on the main floor and let the rest as flats.