Even one day in Madrid is enough to soak up its beauty!
If you like Picasso, and can only go to one museum, go to the Museo de Arte Reina Sofia,Plaza Santa Isabel,52 - 28012 MADRID Tlfs: (+34) 91 -774 10 00 it is across the street from the Prado. the Reina sofia has Picasso's Guernica
and some of his other works. It is a museum of modern art.
Here is a link: museoreinasofia.mcu.es/