The Alcázar of Toledo is a stone fortification located in the highest part of Toledo. Once used as a Roman palace in the 3rd century, it was restored under Charles I (Holy Roman Emperor Charles V) and his son Philip II of Spain in 1540. In 1521, Hernán Cortés was received by Charles I at the Alcázar, following the conquest of the Aztecs by Cortes. Today it houses the Regional Library of Castilla-La Mancha and the Ejército Museum, the latter previously housed in the Salón de Reinos in Madrid.
I recommend photographing the Alcazar from the Mirador del Valle. The view is simply stunning.