The Citadel of Calais was built between 1560 and 1571 on the site of a former medieval castle which was built in 1229 by Philippe de Hureprel. Its purpose of its construction was to fend off would-be invaders, but it wasn't long until the city was successfully invaded by Archduke Albert of Austria on 24 April 1596. Both Louis XIII and Cardinal Richelieu at one time considered expanding the citadel and Calais into a great walled city for military harbour purposes but the proposals came to nothing.
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.