Surroundings of Segovia: Real Sitio de La Granja (Palace and gardens) and a day hiking in the mountains.
Madrid and its Museums: El Prado, Museo de Arte Contemporáneo Reina Sofía, a walk arround downtown Madrid.
Surroundings of Madrid: Monasterio de El Escorial, Valle de los Caídos.
Toledo: Catedral, visit through the multicultural city of Toledo.