A home for a choir
The Orfeó Català, a choir founded in 1891, wanted its own hall. Barcelona's businessmen and music lovers paid for it, and it opened in February 1908.
Built between 1905 and 1908 by Lluís Domènech i Montaner for a Catalan choir, the Palau de la Música is a concert hall where almost every surface is glass, mosaic or sculpture. It's a UNESCO World Heritage Site.

The Orfeó Català, a choir founded in 1891, wanted its own hall. Barcelona's businessmen and music lovers paid for it, and it opened in February 1908.
In the middle of the ceiling hangs a huge stained-glass skylight that bulges downwards like an upturned dome, letting daylight into the hall.
The back wall of the stage is decorated with figures of muses, half sculpture coming out of the wall and half mosaic, as if the music were bringing them to life.
Lluís Domènech i Montaner, one of the leading architects of Catalan Modernisme. It was built between 1905 and 1908.
Yes, with a guided tour. Check the official site for times and languages.
Yes, since 1997, together with the Hospital de Sant Pau, also by Domènech i Montaner.