Edificio Castelar, Madrid, Office building in Salamanca district, Madrid, Spain.

The Castelar Building is an eleven-storey office block at 50 Paseo de la Castellana, on Plaza de Emilio Castelar. Its entrance is a stairway of travertine marble, and the characteristic element is a hanging structure at the rear, paired with a second glass facade that increases daylight inside. Half of its floor area cantilevers, held by stayed cables from a single off-centre concrete core.

Rafael de La-Hoz Arderius designed the building in 1975, assisted by Gerardo Olivares and his son Rafael de La-Hoz Castanys; construction ran from 1977 to 1983. It was built as the headquarters of Banco Coca, which disappeared after merging with Banesto, and later passed to Banco Español de Crédito and then Mutua Madrileña, which leased it to Catalana Occidente until 2009. The son remodelled it between 2010 and 2011, and in 2022 a procedure began to declare it a monument.

The building takes its name from the Plaza de Emilio Castelar on Paseo de la Castellana, named after the 19th-century politician and president of the First Spanish Republic. Since 2012 the entire building has been leased to the law firm Pérez-Llorca, which moved its headquarters here from Calle de Alcalá, 61. The travertine marble staircase at the entrance is the element a visitor can see from the public approach.

The building is accessible from Paseo de la Castellana and sits near major transit connections, making it easy to reach by public transport. Visitors should know that this is primarily a working office complex, so access to many areas may be restricted.

The building avoids internal support columns by using hanging floor plates suspended from the central concrete skeleton. This unusual construction method creates remarkably open office spaces that were innovative for the time.