Swedish divers have discovered thousands of timber piles sunk into the seabed to form a series of barricades. They were intended to block the entrance to the River Lyckeby 1000 years ago – but now the archaeologists are wondering exactly who they were designed to keep out.
The barrier was made with wood now known to have been cut from trees in the winter of 1113 and erected in the Baltic Sea near Karlskrona. The coastal city in the south-east of Sweden is where the country’s last remaining naval base and Coast Guard base are located today.
The discovery was made by scuba divers from Vrak (Wreck), the new marine archaeological museum in the capital, Stockholm.
Last spring Vrak’s archaeological divers had examined ancient remains in Lyckeby Bay, north of where a presumed 12th-century barrier system had been found in 1995. The divers established that the six piles formed part of another such system, lying between two islands.
Later, while searching for a wreck near the islands, they were surprised to come across what they described as a “forest” of heavily eroded oak piles. “It was incredibly cool to discover an unknown pole barrier that was so intact,” said scuba diver and marine archaeologist Jim Hansson of Vrak. Samples of the wood were taken for dating.
Shipwrecks and other historical remains can be unusually well-preserved in Baltic waters, which are too brackish to support shipworms and other wood-boring organisms.
The oak turned out to have been split in such a way that the structure of its fibres, and consequently its strength, had been maintained.
“It made us realise that the barrier must be very old, considering that oak became increasingly rare during the 16th and 17th centuries and onwards,” said Hansson. “Thousands of piles blocked the strait towards Lyckeby, and the fact that they built such extensive barriers shows the importance of the area.
“One can assume that there has been activity there since the end of the Viking Age [around the middle of the 11th century]. Perhaps it was iron exports they wanted to protect – or was it protection against pirate attacks?”
Other well-preserved Baltic discoveries by Jim Hansson and his dive-team reported on Divernet in recent years have included two 17th-century wrecks in 2021; two 17th-century warships in 2019 and a mediaeval cog in 2018.
Vrak, part of Swedish National Maritime & Transport Museums, was built to preserve and spread information about the Baltic’s cultural heritage. Its scheduled opening in 2020 was marred by the coronavirus pandemic, but the museum has recently reopened fully to visitors on every day of the week and Wednesday evenings – find out more at the Vrak website.