The Saint-Philbert-de-Grand-Lieu abbey was constructed around 815 on the lands of a former estate called Déas, which were given to the monk Saint Philibert in the 7th century. It was affiliated with the Abbey of Noirmoutier and served its needs. The construction was authorized by Louis I, the son of Charlemagne. This location was chosen because it was more protected from Viking raids, being further inland. Indeed, the Abbey of Noirmoutier had been attacked by the Normans multiple times during the first half of the 9th century.
During the 14th century, a wooden bell tower was erected above the entrance porch of the abbey. During the religious wars in the region, the Huguenots also caused damage to the site. They notably damaged the choir, the porch, and the bell tower. In the 17th century, the church became a parish church. Later, during the French Revolution, the abbey was sold as national property in 1791. During the Vendean uprisings, the building was used by the republicans as a fodder shed and a munitions depot.
After the construction of the new parish church in 1869, the abbey served as a covered market, and the cracked walls had to be reduced in height by 3 meters. However, the discovery of the tomb in 1865 eventually renewed interest in the site, and restoration work was carried out between 1898 and 1904. Consequently, the abbey has been classified as a historical monument since 1896, even though it was no longer in use. It was only in 1936 that it was returned to religious use. In the same year, a celebration marked the 1100th anniversary of the transportation of the relics to the town, and a relic of Saint Philibert was placed in the sarcophagus. The monument is now open to visitors, with approximately 9,000 visitors per year. In addition to tours of the building and gardens, artistic and cultural exhibitions are held within the abbey. Religious ceremonies are occasionally celebrated, including the 'Feast of Saint Philibert' with a vigil and a patronal Mass.
The abbey is predominantly in the Carolingian style, but modifications over time have incorporated elements from other styles, including Romanesque. The building has also undergone changes in its visual appearance, both on the exterior and interior.
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.