Two thousand years! I thought of the stone ships too (these are burials marked by stones laid out in the shape of a ship), but I went searching for an old example and it seemed like the oldest persuasively dated one is from around 600.
Tjelvar on Gotland are presumed to be from 750BCE, and I don't think that is the oldest in Scandinavia.
Tjelvar on Gotland are presumed to be from 750BCE, and I don't think that is the oldest in Scandinavia.