Remains of the former city wall (4th century) have been preserved from Roman times. The oldest core of Barcelona, the “Gothic Quarter” (Barri Gòtic) with many old houses and palaces (including City Hall, 14th century; Palau del Lloctinent, 16th century; Palau de la Generalitat, 15th century, seat of the autonomous government of Catalonia), extends around the three-aisled cathedral (1298–1448) with a Gothic cloister (14th / 15th century), neo-Gothic west facade (1898) and dome tower (1913), which was built in place of a Romanesque predecessor. The Palau Reial Major (14th-18th centuries) is home to the Gothic chapel of Santa Àgata (beginning of the 14th century, altarpiece by J. Huguet) connected; the Tinell Hall (1359–70, former royal ballroom) has six round arches and a five-storey gallery called Torre del Rei Martí. The Episcopal Palace (inner courtyard with two Romanesque arched galleries), mentioned in a document as early as 926, was renovated in the 19th and 20th centuries. After I. Cerdà i Sunyer’s urban expansion (1859), the modern cityscape was mainly shaped by three events: the world exhibitions of 1888 and 1929 and the 1992 Olympics. The time of Barcelona as the center of avant-garde architecture in the 1930s with the architects’ association GATCPAC (since 1930) and designs by Le Corbusier, the Plan Macià and the Casa Bloc (1932–36) by J. L. Sert are particularly reminiscent. The greatest urban development at the end of the 20th century was the opening of the city to the sea by removing the railway systems and expanding the shore zone.
Other buildings: Romanesque church of Sant Pau del Camp (10th century, expanded in 1120), three-aisled church of Santa Maria del Mar (1329–83, with ambulatory and magnificent rose window), Palace of the Viceroy (1773–76), Llotja (the stock exchange, 18th century, built around the still completely preserved Gothic stock exchange hall, 1386). The most important modern sacred building is the Temple de la Sagrada Família, designed primarily by A. Gaudí (begun in 1883, unfinished; construction continues to this day).
In 2005, parts of the building (nativity facade, apse facade, crypt) were added to the UNESCO World Heritage List as an extension of the “Works of Antoni Gaudi” world heritage site. The church was founded on November 7, 2010 by Pope Benedict XVI. consecrated and raised to the rank of Basilica minor (basilica). The buildings also created by Gaudí Casa Milà (1905-10), Palau Güell (1885-89) and Park Güell (1910-14) were declared a World Heritage Site by UNESCO.
Other spectacular buildings in the style of Modernism are the Palau de la Música Catalana (1905-08) and the Hospital de Sant Pau (1902 ff.) By Lluís Domènech i Montaner, both also UNESCO World Heritage Sites, as well as the so-called »apple of contention« (» Mançana de la Discòrdia «), a group of three houses by different architects on Passeig de Gràcia. – Barcelona’s chessboard-like new town (Eixample) consists of regular, multi-storey building blocks (Illes), mostly truncated at the corners. The centers of urban life are the “Rambles”, wide avenues of plane trees with flower and bird markets. As part of the “Squares and Sculptures” urban renewal program in the 1980s and 1990s, which received worldwide attention, around 60 newly designed facilities were created, whose character is based on objects by well-known artists (J. Miró, A. Tàpies, E. Chillida, R. Serra). The conversion of the modernist publishing house Montaner i Simon into the Tapiès Foundation (1989–90) also received a lot of attention. As part of the construction program for the 1992 Summer Olympics, the stadium for the 1929/30 World Exhibition was expanded and the Olympic Village was laid out as part of the expansion project for the entire coastal region of the city. A. Isozaki designed the Olympic sports facility “Palau Sant Jordi” on Montjuïc (1983–90). There is also the former main building of the exhibition center from 1929, the Palau Nacional (today the Museum of Catalan Art). The redesign of the old port is receiving buildings based on designs by Albert Viaplana and Helio Piñón made excellent architectural accents. The numerous new buildings also include the faithfully rebuilt world exhibition pavilion by L. Mies van der Rohe (1929; 1984–86), the Plaça de l’Univers (1991) on the exhibition grounds, the bridge on Felip II Nordbahn (1984–87; S. Calatrava), the Museum of Contemporary Art (1990–95; R. Meier), the telecommunications tower (1989–92; Lord N. Foster), the cultural center (opened in 1994; design by Viaplana and Piñón) and the World Trade Center (opened in 1999; by the New York architectural team I. M. Pei, Henry Cobb, James Ingo Freed & Partners). Other striking new buildings that shape the cityscape are the Edifici Fòrum (2004; converted into the Natural History Museum), designed by Herzog & de Meuron as the seat of the Forum Universal de Culturas festival, and the headquarters of the »Torre Agbar« (2005) designed by Jean Nouvel by Aguas Barcelona on the redesigned Plaça de les Glòries, and the eccentric tower structure “Torre Mare Nostrum” (2006), seat of the headquarters of the Gas Natural group on the Barcelonita peninsula, by E. Miralles (posthumously) and his wife Benedetta Tagliabue. In 2009 Ricardo Bofill’s Hotel Vela am Hafen and the shopping center Les Arenes (Richard Rogers) completed. The restored and modernized market hall “Mercat de Santa Caterina” (2005), a magnet for visitors in the old town, also came from Miralles and Tagliabue.