The city's main attraction is the world famous Monastery of San Lorenzo de El Escorial, (El Escorial for short) , a World Heritage Site, that was the political centre of the Spanish empire when the king was Philip II. It is often visited as a day-trip from Madrid, however it's a good place to spend 2 or 3 nights, because it is located in a beautiful natural place.
Monastery of San Lorenzo de El Escorial: This huge complex is has a Royal Palace, a monastery for monks, a magnificent library, and a large basilica. Kings of Spain are buried in the Kings' Pantheon. It also have an important collection of paintings by Van der Weyden, el Greco, Tintoretto, Veronés or Velázquez.