Recinto Modernista de Sant Pau is one of the finest examples of Catalan Art Nouveau architecture in the world, designed by Lluís Domènech i Montaner and built between 1902 and 1930. The complex was a functioning hospital until 2009; today it operates as a UNESCO World Heritage Site open to visitors.
The buildings are extraordinary: exposed brick facades covered in polychrome ceramic tiles, mosaics, and sculptures by Pau Gargallo. The grounds are also carefully landscaped. Free guided tours run daily (advance booking advised). Address: Carrer Sant Antoni Maria Claret 167, a short walk from the Sagrada Família.