The Alhambra in Granada, Spain was first a fortress, and then a fairy-tale palace built as a citadel on a hill by the Moorish rulers of Andalusia. Conquered by Ferdinand and Isabella at about the time Columbus sailed the to the “new” world, the place fell into neglect until it was rediscovered by the romantic movement (and the author Washington Irving) in the early 1800s. Alhambra, California is named after this place, and the genuine Alhambra in Granada is today one of the most popular tourist attractions in Spain.
The Holy Roman Emperor Charles V was also the King of Spain, and ruled the largest empire in terms of land mass of all times. He ordered an imperial palace to be build within the footprint of the Alhambra.
The exterior of the Palace of Charles V is massive. It is fairly regular and unspectacular on the outside, and seems (unsurprisingly) quite imperial in its aesthetic. What is unusual is the curvilinear nature of the interior courtyard putting the building (as Wikipedia puts it) in the avant-garde of its time. You can see the image of the Palace of Charles V above in a larger size by clicking on it.