Late Bronze Age burial sites discovered in Danish forest using ground-penetrating radar

Three new burial sites have been discovered underground on the Danish island of Bornholm, likely dating back to the late Bronze Age. These unusual findings were uncovered in April at a cemetery with over 60 standing stones in the small Gryet forest outside Nexø.

As the sites were found underground and have not yet been excavated, it cannot be definitively concluded what the burial structures consist of. However, based on geophysical measurements, it is likely they are elongated earthen mounds with stones. These types of structures are very rare, as most have been destroyed by cultivation or ploughing. As a plough can reach up to 20 to 40 centimeters deep, it can wipe out any evidence of such structures. Therefore, it is only in untouched forests where there is a chance to find them.

The largest find is 26 meters long and 4.5 meters wide. All were discovered using ground-penetrating radar – a geophysical method that, unlike excavation, does not disturb the ground. The process can be compared to people undergoing X-ray examinations instead of invasive surgery.

The discoveries were made by two geophysicists from Vienna, Austria. In addition to examining the findings, the Bornholm Museum has participated in preparing the site for the geophysicists to work. The Danish Nature Fund, which owns the Gryet forest, funded the measurements.

Among other tasks, trees lying on the ground surface had to be removed so as not to interfere with the machine used for measurement, which needed to make contact with the ground.

The next steps regarding the work with the new finds are currently unclear. As archaeologists, there is a desire to dig as much as possible to gain new knowledge. For instance, there is interest in determining whether there are remains of the deceased or charcoal from a funeral pyre, which could help date the graves more accurately. However, each excavation also disturbs the ancient monuments that should be preserved for the future.

According to the chief archaeologist, the finds can likely be dated to the late Bronze Age based on existing knowledge of such burial forms in the Baltic Sea areas where there are dated finds. He further shared that there are about 30 similar burial constructions known on Bornholm, but only a few in the rest of Denmark.