Josep Batlló hired Gaudí to remodel Casa Batlló, the center building, and to divide it into apartments. Gaudí added a fifth floor, completely revamped the interior, depressed the roof, and added a new façade. The enlarged windows and thin columns inspired the nicknames Casa dels badalls (House of yawns) and Casa dels ossos (House of bones), respectively.
The stone façade is decorated with colored glass fragments, ceramic circles, and mask-shaped balconies. The undulating, scaled roof suggests a dragon's back.
Casas Batlló and Mila, designed by Gaudí within the space of a few years, are on the same street and share some typical Gaudí features:
- wavy exterior walls
- "scooped out" windows