The Palais des Papes (アヴィニョン教皇庁 Avuinyon Kyōkō-chō?, lit. "Avignon Holy See"), also known as the Palace of the Popes (教皇庁宮殿 Kyōkō-chō Kyūden?) is a historical palace in Avignon, southern France. One time fortress and palace, the papal residence was the seat of Western Christianity during the 14th century due to the Avignon Papacy. During the Academy City invasion of Avignon a third of the palace is destroyed by the use of HsB-02's Earth Blade.
The inside of the palace is vast, giving one a feeling of lonely isolation. There is apparently nothing inside the palace by early October of the timeline. The walls did not have any wallpaper, just bare stone. Other than the evenly spaced pillars holding up the ceiling, nothing was there.
Avignon was apparently built around the Palais des Papes according to Itsuwa. At the end of the 13th century, there was a dispute between the Roman Catholic Pope and the French king. And the winner of that dispute was the French king. He gained the right to order around the Pope at the time. One of his orders was for the Pope to leave his headquarters and come live in France. Thus beginning the Avignon Papacy starting in the early 14th century. According to Itsuwa, apparently the French wanted to control the Pope in order to use the various privileges and benefits the Roman Catholic Church had. Avignon was chosen as the place to imprison the Pope. And the palace the Pope was imprisoned in what is now known as Palais de Papes, and reigned there starting from 1309 up until the last one left for Rome to continue his papacy in 1376.