The Palacio Real on Plaza de San Pablo was where Philip III moved the entire royal court between 1601 and 1606, briefly making Valladolid the capital of the Spanish empire. Earlier it had been a great noble residence; Charles V also lived here for spells. The exterior is austere, the patio inside is elegant and Renaissance in style, and the upper floors still retain ornate plaster ceilings.
The palace today houses a military government office and is only partly open to the public, generally for the patio and a few exhibition spaces. Even from the outside it is worth a stop: the square it sits on, with the Iglesia de San Pablo opposite, is the most palatial ensemble in Valladolid.