Siø-dyssen, also known as a Langhøj, is a submerged Stone Age barrow located off Siø,
between Siø and Langeland, Denmark. Dated to the period between 3950 and 2800 BCE,
it represents a “langhøj,” a type of long barrow that was a forerunner to later
Stone Age dolmens (stendysser) and passage graves (jættestuer).
This monument is unique evidence of the significant sea level rise that began around
8,000 years ago during the Holocene transgression, which led to the formation of the South Fyn Archipelago.
Originally built on the southernmost tip of Siø, serving as a prominent landmark for passing sailors,
the barrow gradually became submerged as the sea encroached upon the low-lying areas.
Today, it is typically covered by about half a meter (55 cm) of water,
though stones are partially visible at low tide. All original earth fill has been washed away,
leaving only a few of the large stones that once defined the barrow.
The Siø-dyssen has also suffered damage: in 1916, a substantial portion of its stones were removed
and used for the construction of a steamboat pier on Siø. A museum inspection took place in 1943
after a report from a local merchant, confirming its submerged state and the removal of most of its curb stones,
some of which were up to 1.5 meters high, and any potential burial chambers.
The barrow is part of a broader archaeological and geological landscape in the South Fyn Archipelago,
featuring other submerged coastal settlements and monuments that highlight a rich prehistoric life before rising sea levels.
www.kulturarv.dk/fundogfortidsminder/Lokalitet/113353/
www.langeland.dk/langeland/planlaeg-din-tur/sioe-dyssen-gdk1130402