The Aljaferia Palace is a fortified palace that was built during the second half of the 11th century in Zaragoza by Abu Jafar Ahmad ibn Sulayman al Muqtadir billah (1046/7-1081/82), as the residence of the Banu Hud dynasty. It was originally named "Dar al Surur" ("House of Joy"). The name Aljaferia derives from "al-Jafariyya", after the name of its founder. The structure holds unique importance in that it is the only conserved testimony of a large building of Spanish Islamic architecture in the era of the Taifas (independent Islamic kingdoms). The most remarkable feature of the Aljaferia is in the systems of interlacing arches with a high degree of complexity. In 2001 Aljaferia Palace was added to the category of Mudejar Architecture of Aragon, that was declared World Heritage by UNESCO.