Found at number 43 on the prestigious avenue of the Passeig de Gracia, the Casa Batllo was built between 1904 and 1906 by Gaudi for the industrialist Josep Batllo. Listed as a UNESCO World Heritage Site, the building seduces visitors with its spectacular modernist architecture and a profusion of visual effects. Passers-by are attracted by the irresistible exceptional polychrome façade decorated with mosaics and plant motifs, with a wavy ceramic roof that evokes the sea. The artistic use of materials and colours recreate the light and transparency of the Mediterranean sea: a house straight out of a fairy tale! Recently, for its centenary, the top floor and terrace of this wonderful building were opened to the public.