Augustae was built as a fortified military camp in the mid-1st century, as the first fortification was made of wood and earth. The castle was naturally protected to the south by the Ogosta River, to the east and north by marshland. Access was possible only from the western side, where a fortified wall reinforced with a ditch was erected. In the 2nd-4th century Augustae developed as a Roman and an early Byzantine urban centre. Its total area reaches about 9 hа.
The fortress had the shape of an irregular pentagon extending from north to south. The fortress wall was dug inside up to 2.30 m and its thickness reached 2.50 m. Its walls were made of roughly worked stones, bonded with white mortar. The fortress had three gates - one to the west, north and east. The defence system consisted of protruding towers. The necropolis was located west of the fortress. Archaeologists have uncovered the fortification system of the Early Roman camp and the settlement dating to the Late Antiquity. The western wall with three rectangular towers and the western gate of the stone fortification have been explored. The site of the severely destroyed northern gate has also been established. Buildings have been uncovered in the inner part of the site, located in the approximate centre of the early Roman camp. In the 3rd–4th century the city was restored periodically after the invasions of the Goths. The last destructive invasion by the Avars in the 6th century marked the end of its existence.
References:Visby Cathedral (also known as St. Mary’s Church) is the only survived medieval church in Visby. It was originally built for German merchants and inaugurated in 1225. Around the year 1350 the church was enlarged and converted into a basilica. The two-storey magazine was also added then above the nave as a warehouse for merchants.
Following the Reformation, the church was transformed into a parish church for the town of Visby. All other churches were abandoned. Shortly after the Reformation, in 1572, Gotland was made into its own Diocese, and the church designated its cathedral.
There is not much left of the original interior. The font is made of local red marble in the 13th century. The pulpit was made in Lübeck in 1684. There are 400 graves under the church floor.