Official name is Borgring
Borrering also known as Vallø Borgring or Vallo ring-fortress is a Danish Viking fortification located on Zealand, east of Gammel Lellingegaard in the parish of Højelse and north-east of Lellinge. The ring sits on land under the Chapter of Vallø.
Wikipedia https://en.wikipedia.org/wiki/Borrering
Address 4600, Denmark
Coordinates 55°28'10.853" N 12°7'20.655" E