The lordship of Sigournais has existed since at least 1050. It was then the property of Zacharie de Pouzauges, a vassal of the vicomtes de Thouars. In the 12th century, a priory dedicated to Saint-Saturnin was built within the walls of the castellum. Issues of cohabitation with the castle's inhabitants arose. Moreover, the current castle, built by Guyard de Sainte-Flayve, came into existence thanks to the relocation of the priory outside the enclosure.
Nothing remains visible from the ancient fortress of the 12th century; the foundations in the ground are located a bit further to the north, with the current castle covering a part of them.
The current castle, constructed under Guyard de Sainte-Flayve, dates from the late 15th century and has an almost pentagonal shape. This enclosure consists of curtain walls flanked by eight round towers and a large gatehouse tower. A dry moat carved into the limestone surrounds it all. The gatehouse tower serves as both a fortified entrance (gatehouse) and a main tower (keep). It consists of a large rectangular tower flanked by two round towers on each side, all crowned with a battlemented walkway on machicolations. The entrance corridor is divided into two entrances, one for carts and one for pedestrians. On the outside, a fixed bridge was extended by a cart bridge and a pedestrian drawbridge, side by side. Inside the gatehouse tower, there were two levels. On the first level, there was a guard room and a vestibule. Canon openings were arranged in the thickness of the wall. On the second level, accessible by the spiral staircase in the South flanking tower, there was a room serving both as a reception hall and as the lord's residence, separated by a wall was a chamber.
A large pentagonal courtyard was protected by walls and towers, crowned with crenellated battlements on machicolations, and probably served as a bailey (outer courtyard). Some buildings were attached to the ramparts, such as stables, kitchens, a bakery, forge, etc.
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.