Casa Batlló (1904-6) was converted from an existing apartment building (1877) when it was bought by textile merchant Josep Batlló i Casanovas, the work carried out by Antoni Gaudí (1852-1926) and Josep Maria Jujol (1879-1949) (who assisted Gaudí on many projects such as the work in trencadís in Park Güell). Gaudí redid the entrance lobby, interior well and all the rooms, transformed by curves and vortices into cavernous spaces. Light is encouraged to come in through the windows by glasswork and mirrors. The stairwell avoids the usual sharp transition from glare to gloom by the changes in texture and colour: the walls attain greater colour luminosity as they descend and become more textured in order that light be diffused and held. The windows looking onto the well decrease in size from top to bottom. The effect is that the view from the top floor down the well gives the appearance of walls uniformly coloured and lit and the depth uncertain without the plunge of perspective and diminishing light.
Gaudí and Jujol collaborated on the facade that looks on to Passeig de Gràcia, whose skeletal forms earn the building the sobriquet of casa dels ossos. Ovate stone apertures on the first floor are propped on femurs and tibias. The mosaic-covered wall rises above the piano nobile, culminating five floors up in the vertebrae of a scaly dragon-like back. The mosaic in blue, green, grey and white, punctuated by larger rounded ceramics making highlights, takes on different hues according to the way light strikes it. The building is intentionally monstrous, its symbolism from the legend of Catalunya's Saint George. Robert Hughes - Barcelona, 1992, ch. 8, VII - elaborates. The bone-like forms were echoed by Gaudí's furniture designs for Batlló's dining room, now removed, along with most of the other furniture, to leave space for the wandering tourist.