The ruins of Illens castle stand on a rock wall above a loop of the Saane river. The castle stands on the opposite side of the river from the fortified town of Arconciel. The two castles secured both sides of a crossing (either a ford or a bridge) over the river. The castle is first mentioned between 1150 and 1276.
In 1366, the notoriously violent Count Peter of Aarberg moved into the castle and remained there for a short while. The chamberlain of Charles the Bold, Guillaume de la Baume, expanded the castle and when he left in 1470, it was an elegant and comfortable palace. During the conflicts leading up to the Burgundian Wars, Fribourg and Bernese troops stormed and damaged the building on 3 January 1475.
In 1900, it was partly repaired and expanded and served a community of Trappist monks.
References:The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.