Thanks yet again to Jose, I now know this is the Palau Baró de Quadras, designed as a refurbishment by Josep Puig i Cadafalch in 1902-1903. Many details, such as the mosaics, sgraffito work and multi-coloured woodwork, are reminiscent of the Arabesque neo-Mudéjar style.

Around back (and across the street, in Riyadh), posted earlier: