Located on the plot where the former palace of the Dukes of Osuna once stood, next to the Jardín de las Vistillas, this building was designed by architects Miguel de Olabarría and Ricardo García Gueret, who began work on its construction in 1902. It is one of the most interesting Neo-Mudejar constructions in Madrid in terms of its size, reminiscent of military architecture, and its exposed brick facades, dotted with large window openings. 

This rectangular building has turrets on the corners and an entry tower on the east side. It is distributed symmetrically around two rectangular courtyards. The central section, which stands in between the two courtyards, is occupied by the church. The floor plan is in the shape of a Latin cross and has just one nave. The seminar was completed by García Guereta and Juan Moya, after the death of Olabarría in 1904, and it was eventually inaugurated on 23 October 1906.

Nowadays, as well as being home to the seminary of the archdiocese of Madrid, it also houses the San Justino Faculty of Christian and Classical Literature, part of the San Dámaso Ecclesiastical University.