Gävle Castle is the northest one of so-called Vasa castles, built by Gustav Vasa of Sweden or his sons. The construction started in 1583 by the religious King John III of Sweden. The design was made by Willem Boy and the center of castle was a chapel. The castle was completed in 1597, five years after John's death.
In 1727 the chapel and the top floor were destroyed by fire. Gävle castle stayed damaged until 1741, when it was agreed to rebuilt. The current appearance dates from the design made by Carl Hårleman. In 1754 the reconstruction was complete.
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.