This palace completed [Baroque#ESCUELAS#73] Madrid's set of royal residences. It was built in the 1630s in a succession of uninterrupted stages at the Count-Duke of Olivares' frenetic pace, who was the real force behind the project. It was not built to replace the old Renaissance [Royal Palace#MONUM_enENTOS#16], but rather to be used as a leisure residence by Philip IV. This was why it was situated in the Prado de San Jerónimo, an area where the inhabitants of Madrid went for walks and the nobles had small places with gardens where they gave parties. The building, which started off as a timid remodelling of the Cuarto Real de San Jerónimo became a large palatial complex, with extensive gardens dotted with shrines and a lake big enough to hold staged naval battles. Today we can still admire a large part of these gardens as they form the Retiro Park in the city. Improvisation in its construction influenced the ground plan design and the building's outer appearance, built basically in poor quality brick. However, the interior decoration more than compensated for this, with its extraordinary art collection, much of which was commissioned at the time. The building was seriously damaged during the Napoleonic invasion; it was fortified by the French and then was finally destroyed. Only two parts have survived, although somewhat modified: the Salón de Reinos, the most important room because of its decoration, which housed the Museo del Ejército up to 1998; and the ballroom, today known as the Casón del Buen Retiro, which forms part of the Museo del Prado.