It was completed in 1584 and was built as a summer retreat for King Phillip II, and some retreat !!.It was the work of Juan Bautista de Toledo and Juan de Herrera being built to commemorate the victory over the French in 1557. The interior was completed at the beginning of the 17th Century and the shear size of the place was meant to measure the importance of the Spanish empire of the time whilst humbling visitors at the same time, which of course it does to this day.
For visitors the El Escorial Monastery is an historic monument that really delivers on all fronts as it offers so much. It is simply awash with fantastic sculptures, tapestries and paintings not to mention the stunning royal mausoleum which houses the tombs of the Spanish Monarchs, quite amazing to think that all the kings since Charles I of the last 500 years are buried here, except Phillip V and Ferdinand VI.
Here is the official web site for the Escorial Monastery