Sisteron Cathedral, now the Church of Notre-Dame-des Pommiers, was formerly a cathedral, and is a national monument.
The cathedral, dedicated to the Blessed Virgin Mary and Saint Thyrsus, was the seat of the Bishops of Sisteron, who had a second seat at Forcalquier Cathedral. The bishopric was abolished under the Concordat of 1801 and merged into the Diocese of Digne.
The Romanesque building, one of the most sizeable religious structures in Provence, was built between 1160 and 1220.
Celje Castle was once the largest fortification on Slovenian territory. The first fortified building on the site (a Romanesque palace) was built in the first half of the 13th century by the Counts of Heunburg from Carinthia on the stony outcrop on the western side of the ridge where the castle stands. It had five sides, or four plus the southern side, which was a natural defence. The first written records of the castle date back to between 1125 and 1137; it was probably built by Count Gunter. In the western section of the castle, there was a building with several floors. Remains of the walls of this palatium have survived. In the eastern section, there was an enclosed courtyard with large water reservoirs. The eastern wall, which protects the castle from its most exposed side, was around three metres thicker than the rest of the curtain wall. The wall was topped with a parapet and protected walkway.