This palace was conceived as part fortress, part pleasure residence. It has three military-style towers from the 13th and 14th centuries. The Old Palace on the right dates from the 12th century, and the so-called "New Palace" on the left dates from the 14th. It's said that the old, arthritic, and sometimes very overweight archbishops used to be hauled up the interior's monumental Louis XIII-style stairs on mules.
Today the once-private apartments of the former bishops contain three museums. The Musée Archéologique contains prehistoric artifacts, Bronze Age tools, 14th-century frescoes, and Greco-Roman amphorae. Several of the sarcophagi date from the 3rd century, and some of the mosaics are of pagan origin. The Musée d'Art et d'Histoire is located three floors above street level in the archbishop's once-private apartments (the rooms where Louis XII resided during his siege of Perpignan). Their coffered ceilings are enhanced with panels depicting the nine Muses. A Roman mosaic floor and 17th-century portraits are on display, as well as a collection of antique porcelain, enamels, and a portrait bust of Louis XIV. In the Horreum Romain is a labyrinth of underground passageways, similar to catacombs but without burial functions, dug by the Gallo-Romans and their successors for storage of food and supplies during times of siege.