Gaudí's 1914 mosaic-trencadís garden city above Barcelona — community housing turned public park. UNESCO 1984.
From Wikipedia
Park Güell is a complex of parks and gardens in Barcelona with architectural elements, located in the La Salut neighborhood of the Gràcia district in Barcelona, Catalonia, Spain. It is situated on the southern slope of the Turó del Carmel hill, part of the Collserola mountain range, overlooking the city. The separate Parc del Carmel lies on the northern side of the same hill.