The Mount of El Pardo was an extensive open area known to be a royal hunting ground since the time of Alfonso XI (1342). The emperor Charles V ordered the architect Luis de Vega to build the palace in 1540. It housed a splendid collection of paintings and was one of the first buildings with a slate roof anywhere in Spain. The Imperial Coat of Arms is still visible on one of the corners of the building. The palace as we know it today is the result of the extension work carried out by King Charles III. Francisco Sabatini was the architect in charge of the project, and he doubled the size of the existing palace by creating a central courtyard. Today, the Royal Palace of El Pardo is also used as a residence for foreign heads of state when on official visits to Spain.