The triangular-plan building occupies a 16,416 square metre site. The total built surface is 42,269 square metres, distributed among nine floors.
The areas for document storage (the two equal sides of the triangle) occupies 28,249 square metres, and, instead of being underground (as happens in most cases), they are raised over pilasters in the shape of a stilt dwelling, one of the most special characteristics of the building. Its total capacity for document storage is approximately 200 metres of non-compact shelves.
The decision to build a building with a new layout was made by then General Director of Archives and Libraries, Mr. Luis Sánchez Belda, who based his project on two basic premises: the appropriateness of the structure of the building to the functions of the new archive and collaboration between archivists and architects, which was a milestone for the history of archive facilities. This project was included in the 2nd Economical and Social Development Plan, and it favoured the contribution of unusual investment in this area, with decisive results that laid the foundations of the pre-eminent role of Spain in the international context.
The new building project was carried out by the architect Mr. Juan Segura de Lago, and works began in late 1969.
The first documents were deposited by the end of 1972, although the works did not finish completely until the spring of 1973.