The city of Trelleborg emerged on the beach ridge right next to the sea. The ridge was penetrated by rivers and streams that eventually reached the Baltic Sea. Behind the beach ridge, ponds and lagoons were formed. The rivers and ponds that framed the old Trelleborg can be seen on older maps and are evident in today’s neighborhood and street names, such as Valldamsgatan. Behind the beach ridge, there were two elevated plateaus. The larger one, called Kattebäckshejdan, has been investigated by archaeologists on several occasions. It is on this elevation that the Viking fortress was discovered, and it is also where Trelleborg with the Viking Museum is located today. On the smaller elevation, a church was built in the 13th century, and this church still stands today, although heavily rebuilt.
The archaeology on the larger of the elevations is most famous for the Viking fortress discovered in the late 1980s. However, the site also concealed remains from other time periods. Tools made of flint, grinding stones, ceramics, and pits from the Neolithic period were found here. During a part of the Bronze Age, there was a house estimated to be 26 meters long and 7 meters wide. Ceramic artifacts, roughly worked flint, parts of grinding stones, and two graves dating back to the Bronze Age were also discovered in the area. One of the graves contained a remarkable bronze dagger.
It was during the later part of the Iron Age that the settlement grew significantly and left abundant remains in the form of postholes from houses, hearths, pits, and objects. The Viking Age fortress seems to have largely replaced this settlement, at least on this elevation. The reason for choosing to build a fortress on this elevation remains somewhat of a mystery. Was this one of Harald Bluetooth’s ring fortresses, a so-called Trelleborg, built with the purpose of unifying and Christianizing Denmark? One thing is certain, the fortress was constructed in a well-chosen location near the Baltic Sea. The strategic position was likely of interest to both regional and local power elites.
Trelleborg seems to have been abandoned as early as the beginning of the 11th century. After the fortress was abandoned, the area appears to have been uninhabited and relatively devoid of activity for 200 years, only to flourish again during the 13th century and onwards with extensive medieval urban development. Archaeologists have found several traces of buildings and objects from the 13th century and beyond. By then, Trelleborg, which inherited its name from the Viking fortress, had become a prosperous medieval town with a marketplace, church, and monastery. In the 14th century, the site of the former fortress began to be populated with longhouses whose gables faced the road that once passed through the fortress. At this time, parts of Trelleborg’s rampart were likely still visible as a boundary leading out of the city to the west.