Casa Batlló is a building in the center of Barcelona. It was designed by Antoni Gaudí, and is considered one of his masterpieces.

The earlier house was redesigned by Gaudí in 1904 and has been renovated several times since then. Like everything Gaudí designed, Casa Batlló can be defined as modernism in the broadest sense. This unique design was inscribed on the UNESCO World Heritage List in 2005, along with other works by Antoni Gaudí.

The façade consists of three harmoniously integrated parts. The main floor, the lower ground floor, and the galleries on the first floor are set within a Montjuïc sandstone structure with undulating lines. The central part is a multicolored section with projecting balconies. The top of the building is a gable-like crown, level with the roof, which helps to hide the room where the water tanks used to be located.

The building has a skeletal organic quality, hence its local name Casa dels ossos [House of Bones]. The ground floor is particularly impressive with its tracery, irregular oval windows and fluently chiseled stonework. A large part of the façade is decorated with a mosaic made of broken ceramic tiles [trencadís], starting from golden orange tones and progressing to greenish blues.

Above the central part of the façade is a smaller balcony, also in iron, with a different exterior aesthetic, closer to a local species of lily. Two iron arms are placed here to support a pulley for raising and lowering furniture.

The roof is arched and resembles the back of a dragon or a dinosaur. The roof terrace is one of the most striking parts of the building because of this design. The roof is adorned with four chimneys designed to prevent backlash.