The document summarizes four famous architectural sites in Barcelona designed by Antoni Gaudí: The Sagrada Familia, a Catholic basilica begun in 1882 that is still under construction and is Gaudí's masterpiece; Parc Güell, a garden complex designed by Gaudí from 1900-1914 that is part of the UNESCO World Heritage Site; The Cathedral of Barcelona known as "La Seu", a famous example of 14th century Catalan Gothic architecture; and La Pedrera, also known as Casa Milà, Gaudí's surprising modernist building constructed from 1906-1912 with a distinctive roof terrace overlooking the city center.