The Heidenmauer ('heathen wall') is a circular rampart or ringwork, two and a half kilometres long, which was built by the Celts around 500 BC. The wooden elements of the wall have disappeared over the course of time by rotting away, but the stones have survived. Copious numbers of pottery finds have enabled a very precise dating. Almost all the containers are hand-made, only a few show traces of having been turned; this technology first appeared after ch 500 BC. in the La Tène period. Other finds included iron, long knives as well as querns, pyramidal stones that were stuck point-down in the ground in order to provide the base for the milling of corn. In addition there is also evidence of milk production and iron smelting.
In the 4th century A. D. a small part of the circular rampart as well as the Kriemhildenstuhl below was used by the Romans as a quarry.
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.