[2][3] In 2023, along with four other Viking ring fortresses, Borgring was isncribed on the UNESCO World Heritage List for its unique architecture and testimony to the strategic and military power of the House of Knýtlinga (Jelling dynasty).

[4] Borgring is circular in shape and spans 145 metres across and thus ranks third among the original, Danish Viking ring fortresses.

Therefore, the versions of the name used by Sophus Müller, Trap Danmark, during the excavations led by Thorkild Ramskou in 1971–72, in the National Museum registry and Harald Andersen are not mentioned.

So, in terms of naming, Borrering becomes part of a group of pre-historic fortifications that include Borremose fortified settlement in Himmerland, Borreknold on Falster and Borrehoved on Bornholm.

[citation needed] The US Air Force aerial photo (ortho-photo) from Basic Cover 1954 and provided by COWI shows the fortress as a somewhat blurry shadow on the field.

[21] It was only after echo-photography in November 1970 that it was suggested there might be an actual trelleborg near Lellinge; the circular structure was recognized on a photography by warrant officer Valdemar Ryhl from Air Base Karup.

[22][23] In 1971–72, the Danish National Museum, represented by Thorkild Ramskou, conducted excavations on the site, but the research technology available at the time left the embankment itself undated.

The Museum registered the ring fortress as Borrering, and when Harald Andersen submitted an article to the magazine Skalk in 1992 in which he "dragged" the pre-Medieval fortifications out of the darkness, Borrering was consequently referred to in this version: On the difficult task of gaining a comprehensive view of pre-historic fortifications Harald Andersen wrote: "A student wishing to attain a complete overview of this material, while circumventing the archives, must traverse the entirety of Trap Danmark, where every Danish fortification is dealt with, if sparsely.

Up until 2014, the location has only been mentioned a few times in literature,[26][30] leaving one of the largest circular fortresses in Denmark in relative obscurity, and just in line with what is known, or not known, about the other trelleborgs.

Despite the geometric plan, the type-marker for a trelleborg, the gates of Borgring are not perfectly aligned north, east, south and west.

The minor dislocation (11°) probably reflects concerns that the fortress would emerge asymmetrical in the landscape if the prevailing building principles were rigorously obeyed.

"The Danish Castle Centre and Aarhus University: Enigmatic Viking Fortress discovered in Denmark" (PDF).

Danmarks Borgcenter: Vallø Borgring – Gådefuld vikingeborg fundet ved Køge Archived 7 September 2014 at the Wayback Machine [in Danish]