Excavations
Trelleborg near Slagelse in West Zealand was the first ring fortress to be excavated. This took place between 1934 and 1942. The name Trelleborg quickly became a term that was also transferred to the ring fortresses found later. However, the term is misleading, and today the word ring fortresses is used.
Aggersborg had long been known, but only in 1945-1952 were excavations carried out. After the completion of these major investigations, smaller, targeted excavations and investigations were carried out at Aggersborg from 1990.
Actual exploratory excavations were carried out in 1990, and then in 2007-2010 search trench investigations and systematic metal detector searches under the auspices of the "Kongens Borgeprojektet".
New investigations were launched in 2012-2014. Search trenches were dug around Aggersborg and a geophysical survey carried out within the ramparts. With a ground radar it is often possible to read changes in the ground below the soil layer, and this can e.g. be wall courses and rearrangements of soil, i.e. post holes from houses, pits and graves. The search ditches were above all an attempt to find Aggersborg's missing burial ground. The results were published in a comprehensive work on Aggersborg: the book: “Aggersborg in the Viking Age” in 2014
This was followed by search trench investigations in 2016, where the older settlement was demarcated to the east, and where it was determined that there could not have been a harbor on the east side of the Aggersborg node, and finally that a rocky seawall formed long before the Viking Age was established. It was located below the settlement and in front of the current Aggersborg farm. The beach edge must have been just outside the seawall.