Dun Ardtreck is a D-shaped dun, or 'semi-broch', situated on a rocky knoll on the edge of a cliff overlooking the sea. It encloses an area of about 13 by 10 metres. It was constructed with a ruidmentary hollow-wall. The entrance is particularly well-preserved with door-checks characteristic of brochs. The entrance to a guard cell led off to the right behind the door-checks.
Dun Ardtreck was excavated by Euan W. MacKie in 1964-1965 as part of an exercise to establish the development of the broch. It had been built in two stages: a roughly level platform was constructed and on this was set the galleried wall. Charcoal from the platform was radiocarbon dated to 115 BC. The first phase of occupation seems to have been very short and it appears to have ended in violence and destruction. The second phase was dated from the pottery finds to the middle of the 2nd century AD. The finds from this period included iron tools, bronze ornaments and glass ring-heads as well as Roman Samian ware pottery sherds and a piece of a Roman bead.
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.