Locations of the fortesses of Aggersborg, Fyrkat, Nonnebakken, Eskeholm and Trelleborg in Denmark, and Borgeby and Trelleborg in Sweden.
The ringfortresses were all build in the years 980 to 981 during the danish King Harald Bluetooth.
Today they are still a mystery what the exact purpose was.
On the hack of both Trelleborgs can be seen a photo how they looked like.
Google Earth Hacks is not affiliated with Google in any way
"Google" and "Google Earth" are trademarks of Google Inc.