In the middle of the Maribo Lakes, from Søholt in the west to Kårup Vænger in the east, one of the largest defences of the Iron Age was built in around 550. Part of the site has been preserved and is now protected.
The defence complex consists of two large separate ramparts. The eastern rampart, Hejrede Vold, was 1300 metres long, while the western rampart was about 300 metres long. The distance between the ramparts is 3.5 km, which means that by building two ramparts of 1600 metres in total, an area of 5 km2 has been protected.
The area within the ramparts was defensible and must have served as a refuge. For a fortress to fulfil its function, it must be possible to get to it quickly. Hejrede Vold is centrally located on the eastern part of Lolland, and if we assume that the population could move at 5 km per hour, one could reach it from most of East Lolland in 3 hours. We do not know where the western part of the island's population would have sought refuge, but one guess is that there was a similar refuge near Vesterborg on West Lolland.
It is not known who the enemy was. Enemies may have come from Falster, Zealand, Funen or from the south. Denmark did not exist as a united country in the Iron Age, and the population did not feel Danish. Throughout Europe, many defences were built at that time, because there was unrest and strife after the collapse of the Roman Empire in the 300s.