| UNESCO World Heritage Site | |
|---|---|
 Aerial view of the Viking ring fortress ofTrelleborg, near Slagelse in Denmark. This was the first discovered Viking ring fortress, and the geometry is clearly visible. | |
| Includes | Aggersborg,Fyrkat,Nonnebakken,Trelleborg, andBorgring |
| Criteria | Cultural: iii, iv |
| Reference | 1660 |
| Inscription | 2023 (45thSession) |
| Area | 51 ha |
| Buffer zone | 16,820.8 ha |
AViking ring fortress,Trelleborg-type fortress, ortrelleborg (pl.trelleborgs), is a type ofcircular fort of a special design, built in Scandinavia during theViking Age. These fortresses have a strictly circular shape, with roads and gates pointing in the four cardinal directions. Inside the fort, each quadrant has one, in a single case four, square blocks of longhouses, completing the geometric symmetry. There are a total of five confirmed Viking ring fortresses at present, located inDenmark (although sites in Sweden and across Northern Europe have similar construction).[1] They have been dated to the reign ofHarold Bluetooth of Denmark, with an estimated near contemporary time of construction c. 980. Their exact historical context is subject to debate. In 2023, the five Danish forts were inscribed on theUNESCOWorld Heritage List because of their unique architecture and testimony to the military power of theJelling Dynasty.[2]
This specific type of fortification was named after the first discovered example:Trelleborg nearSlagelse, excavated in the years 1936-1941. Historically, the nametrelleborg has been translated and explained as ″a fortress built by slaves″, since theOld Norse word for slave wasthrall (The modern word istræl in Danish andträl in Swedish) andborg means fortress or city. The wordtrel (pl.trelle) is also a plausible explanation as it relates to the wooden staves which covered both sides of the protective circular walls.[3]
At the end of the 10th century Harold Bluetooth vied with tribalSaxons, theHoly Roman Empire—at that time governed by the (integrated) SaxonOttonian house—and theSlavicAbodrit andVeleti tribes for the control of the southern region of theJutland peninsula,[4] This area was also the very same region presumed to have been the ancient homelands of theAngles. Harald also had to contend withNorse people exercising coastal raids.[5] At theFirth of Schlei layHedeby, known in the contemporary literary sources asSchleswig, where theDanevirke complex of fortifications stretched across the foot of the peninsula, holding back the hostile hosts from entering the territory, as well as providing a safe trade route viaEjderen from theNorth Sea coastline into Hedeby and theBaltic Sea.
The entire complex of fortifications, bridges and roads, includingRavninge Bridge on the land route towardsJelling, are presumed to have been in the hands of Harold. The fortresses establish a string of strategic points stretching from Aggersborg at the north of Jutland southward acrossFunen to end in Borgring at the east coast ofZealand.[6] They have been dated to the reign of Harold Bluetooth, who held sway until c. 985, where he was ousted by his sonSweyn Forkbeard, who eventually conquered theAnglo-Saxon kingdom ofÆthelred the Unready some years later. This is the apex of theJelling dynasty, its patristic line ending the year 1042 withHarthacnut, son ofCnut the Great, son of Sweyn.[7]
Fortifications of a similar shape and date have been found around other old towns in Scandinavia, includingBorgeby,Trelleborgen, andHelsingborg inSkåne, Sweden, nearAarhus in Jutland, andRygge,Norway[8][9] Other, similar forts across Northern Europe include theWalcheren forts inFriesland (built in the outskirts of theCarolingian Empire, with a similar street orientation), andWarham Camp in England, but these are not considered Viking ring forts as they were likely built at different periods in time.[10][11]
The precise purpose of the fortresses is unknown. Some historians argue that they functioned as military barracks or training grounds bySweyn Forkbeard. However, it is more likely that they were intended as defensive strongholds along strategic trade points and/or administrative outposts of the budding state.[12] Søren Sindbæk has offered the hypothesis that the fortresses allowed local populations to seek shelter within the fortress walls against an enemy while waiting for assistance from friendly forces from afar; this means that the fortresses helped Harold Bluetooth to control vast territory and send his army to a particular part of his territory without worrying that the undefended parts would be conquered or plundered.[13] Others have debated whether the fortresses were defensive structures, military strongholds, or primarily served as barracks, as well as the economic, religious, and symbolic significance of the fortresses.[14]
The fortresses were soon abandoned and never mentioned in the literary sources, effectively creating the enigma now known astrelleborge (Danish plural of 'trelleborg').Nonnebakken was enveloped by the near contemporary municipalbishopric of Odense, while the rest receded into the landscape. The modern discovery of these sites began in the 1930s, with the excavation ofTrelleborg in Denmark. Since then, a total of five sites have been officially accepted as Viking ring fortresses.
During the royally funded research projectKongens Borge (The Kings Castles), in 2010, Denmark applied for the admission of Trelleborg, Fyrkat and Aggersborg asThe Trelleborg Fortresses as a UNESCOWorld Heritage cultural property,[15] It is rumoured, that Denmark and Sweden, perhaps around that time, applied for admission of the Viking ring fortresses, but the records available at the World Heritage Centre cannot confirm that any Swedish ring fortresses were ever mentioned.[16] The fivetrelleborge presently known became theViking-Age Ring Fortresses World Heritage Site in 2023.[2]
Thetrelleborgs had similar design,[17] "perfectly circular with gates opening to the four corners of the earth, and a courtyard divided into four areas which held large houses set in a square pattern."[18] They differ clearly from other fortifications in that region because of their geometrical plan, though they do have some similarities with theFrankish forts atWalcheren. A short exposé over early Viking camps in Scandinavia, by Arjen Heijnis, has turned the picture around, marking out these earlier camps "fundamentally different from later defensive structures (ie. the early castles)."[19]
Another characteristic of the ring fortresses of Trelleborg type is their internal features, consisting of axial roads running between the four gates, a ring road running around the inner side of the rampart and the aforementioned four “squares” with blocks of buildings. One of the aims of the excavation in 2015 was to undertake a specific search for these blocks of buildings, […] But as in the earlier excavations, it did not prove possible to locate the blocks of buildings and the axial roads in 2015 (figure 11). […] the collective archaeological findingsat the present state of knowledge suggest that these structures never existed in the fortress. This conclusion receives further support from the fact that blocks of buildings and axial roads have not, as yet, been found at the newly excavated Borgring fortress either, and they are also missing from the fortresses in Scania […]
The fortresses are sometimes partially encircled by advanced ramparts, though not always circular.[citation needed] It has been said the trelleborgs were measured with theRoman foot and that the pointed bottom of themoats is a Roman trait.[citation needed]
Dating bydendrochronology has found the wood used for the construction of Trelleborg to have been felled in the autumn of 980 and thus being used for building presumably in the spring of 981. The findings indicate a short construction time with no signs of maintenance, leading to the interpretation of only a short use of the buildings, maybe five years but hardly more than twenty. Fyrkat may be a little older, Aggersborg somewhat younger. 2014 brought a corresponding date to Borgring (end of 10th century),[20] and, in 2019, following the geo-radar survey and subsequent excavation, Nonnebakken also was dated to c. 980.[21] In the 2021 application to UNESCO, all five Danishtrelleborgs appear with dates between 970 and 980.[22] Some say the material found at Nonnebakken, Borgring, and the Scandian forts is not suffient for a precise dating.[citation needed] However, the layout of the trelleborgs in their local settings are so similar that it is probable that they were also functionally associated.[23]
At the turn of the century much debate had surrounded the ring fortresses,[24] particularly with emphasis on whether or not to addNonnebakken to the list of recognized trelleborgs.Nonnebakken was accepted as late as 2017,[25] though at that time the archaeologist Mads Runge concluded there were no signs of buildings inside the rampart.[26] When geo-radar technology was applied the following year, evidence of structures inside the fort was found, affirming the site's classification as a Viking ring fortress.[21]
| Name | Inner diameter | Rampart width | Number of houses | Length of houses | Position | Year of discovery | Year of construction |
|---|---|---|---|---|---|---|---|
| Aggersborg | 240 m (790 ft) | 11 m (36 ft) | 48 | 32 m (105 ft) | 56°59′44″N9°15′18″E / 56.99556°N 9.25500°E /56.99556; 9.25500 (Aggersborg) | 975–980 | |
| Borgeby | 150 m (490 ft) | 15 m (49 ft) | 55°45′05″N13°02′12″E / 55.75139°N 13.03667°E /55.75139; 13.03667 (Borgeby) | 1997 | |||
| Borgring | 122 m (400 ft) | 10–11 m (33–36 ft) | 55°28′11″N12°7′19″E / 55.46972°N 12.12194°E /55.46972; 12.12194 (Borgring) | 2014 (1875) | |||
| Fyrkat | 120 m (390 ft) | 13 m (43 ft) | 16 | 28.5 m (94 ft) | 56°37′24″N9°46′14″E / 56.62333°N 9.77056°E /56.62333; 9.77056 (Fyrkat) | 1950 | 980 |
| Nonnebakken | 120 m (390 ft) | 55°23′32″N10°23′17″E / 55.39222°N 10.38806°E /55.39222; 10.38806 (Nonnebakken) | 1953 | 980–1000 | |||
| Trelleborg | 136 m (446 ft) | 19 m (62 ft) | 16 (30) | 29.4 m (96 ft) | 55°23′39″N11°15′55″E / 55.39417°N 11.26528°E /55.39417; 11.26528 (Slagelse) | 1936 | 981 |
| Trelleborgen | 112 m (367 ft) | 55°22′34″N13°08′51″E / 55.3762°N 13.1476°E /55.3762; 13.1476 (Trelleborg, Sweden) | 1988 | c. 800 |
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