The Alcázar of Seville is a royal palace in Seville, Spain, originally developed by Moorish Muslim kings. The palace is renowned as one of the most beautiful in Spain, being regarded as one of the most outstanding examples of Mudéjar architecture found on the Iberian Peninsula. The upper levels of the Alcázar are still used by the royal family as the official Seville residence and are administered by the Patrimonio Nacional. It is the oldest royal palace still in use in Europe, and was registered in 1987 by UNESCO as a World Heritage Site, along with the adjoining Seville Cathedral and the General Archive of the Indies.