Borgboda (also called Borgberget), located in Borge hill, Saltvik, is the largest hillfort in Åland with an area of total three hectares. When it was in use, around 1000 AD, the hill was surrounded by water on three sides. Steep hill was enforced with walls of stone and timber, remains of which can still be seen, along with remains of a few buildings. It is believed that Borgboda was never permanently inhabited, but functioned as a place where nearby people fled to when threatend.
The area near Borgboda s rich with prehistorical sites. There is a large iron age burial ground right before the hill, and sizable bronze age cairns are located just a few hundred meters north of the site.
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.