"Eketorp Fort—a prehistoric ring fort—was completely excavated between 1964 and 1974. The first fort (Eketorp I) was built during the Scandinavian Iron Age (ca. AD 300) near the edge of a lake that had been used for animal sacrifices since the birth of Christ." Source: Penn Museum.
"Around AD 400 Eketorp I was torn down and rebuilt (Eketorp II) as a fortified hamlet with a permanent population of farmers. This phase of the fort has been reconstructed for tourism."
A "period of relative peace" around 650 AD led to the abandonment of Eketorp and many other forts in the region. The fort sat empty for almost a half century, but "the lake outside its walls continued as a sacrificial site up to AD 1000." Eketorp was occupied again around 1170 AD, this time as "a military garrison for heavy cavalry during the formation of the Kingdom of Sweden." The fort was permanently abandoned around 1240 AD.