Hammershus, perched on the cliffs of north-west Bornholm in the Baltic, is perhaps Denmark’s best-known ruin. It was excavated and renovated at the end of the 1800s up until 1940, but the ruined castle is still shrouded in a mystery with significance to the history of Denmark: who actually built Hammershus, and why?
For that reason it has been crucial to date the almost thousand-year-old structure, something archaeologists hope they will now be able to do as the ruins are posed to receive their first proper archaeological excavation.
“We’re aware that the parts of Hammershus we know date from the middle ages, but the burning question is precisely when,” says Nils Engberg, archaeologist with The National Museum of Denmark and leader of the excavation. “Exactly when it was built is of huge importance to the role and significance the castle has enjoyed, so it’s incredibly exciting to find out what the studies will turn up.”
Legend may be more accurate than old archaeologists
According to agent legend, Hammershus was built by Valdemar the Great in 1159.
The theory held by researchers for many years, however, was that the castle was built in 1260 by the local Archbishop Jakob Erlandsen.
According to this theory, the Archbishop built the fortress because his former castle, Lilleborg, was conquered and burned to the ground by the Wend Count Jaromar of Rügen in 1259. Hammershus was then built to protect the Archbishop’s interests on Bornholm.
But this theory was brushed aside in the 1990s by another theory: that Hammershus was built in the early 13th century in an alliance between King Valdemar Sejr and Archbishop Anders Sunesen as part of their joint crusade against the Wends.
Excavation leader Engberg says, however, that the archaeological excavation at Hammershus could well support the ancient legend.
“But perhaps Hammershus was built as early as the early Valdemar period (1157-1241) when the crusades began under the leadership of Valdemar the Great and Archbishop Absalon. Which means it simply has to have been the kings who took the initiative of building the fortress,” says Engberg.
He hopes they will find fragments of the old load-bearing oak beams beneath Hammershus. Oak is one of the best materials when it comes to radiocarbon dating. If this is not successful, the researchers will have to piece together a picture using ancient coins and pot shards or the like.
Why dating has to be done under the ground
“But you can take samples from the oldest mortar and try to date the carbon particles in the mortar. However, this method has not yet been fully developed and is still far too uncertain,” says Engberg.
Ancient legend may have a grain of truth in it