The remodelling and modernization of a building between two others for commercial use and housing, for the textile industrialist Josep Batlló, located on the most cosmopolitan street of the city. Along with Casa Amatller (Josep Puig i Cadafalch, 1899-1900) and Casa Lleó Morera (Lluís Domènech i Montaner, 1903-1905) it makes up “the block of discord”, so called because a single block of buildings has three artistic solutions from the same time period, but with different aesthetics.

For Casa Batlló, Gaudí tore down the whole main facade of the old building and built a new one, with fluid shapes, sinuous undulations, and an elaborate outer covering of glassy trencadís that shines with differing intensity according to the way the sunlight hits it. The building consists of seven levels (basement, ground floor and mezzanine, four floors, and attics). On the mezzanine, destined for the residence of the owners, a large gallery juts out, with bony, naturalistic shapes that are very expressive; it includes a guillotine-type window with an ingenious system that allows it to be opened completely.

The architect also made the interior patios of the old building larger, in order to allow air and light to enter, through a large, central skylight that illuminates the interiors all the way down to the ground floor. He also remodelled the back facade, planning a new distribution of the flats and building a new roof with parabolic arches covered with large ceramic scales in various colors, finished with a four-armed cross.

Gaudí paid special attention to the Batlló residence: he invented ingenious tricks for good lighting and ventilation for the spaces, made the ceilings and walls without solutions of continuity, and designed the furniture, from the doors, to the tables, chairs, easy chairs, and even the home's private chapel.

In order to carry out his project, he relied on the collaboration of the architects Domènec Sugrañes, Josep Canaleta, Josep Maria Jujol, and Joan Rubió, the sculptors Llorenç and Joan Matamala, Josep Llimona, and Carles Mani, the Badia wrought iron workshop, the carpentry workshop Casas i Bardés, the Pelegrí stained-glass workshop, and the ceramic products of the factories La Roqueta de Mallorca and Hijo de Jaime Pujol y Bausis in Esplugues de Llobregat, among others.

Casa Batlló has been restored on various occasions and, although it currently remains a private building, some parts can be rented for private acts.

Cultural Item of National Interest since 1969.