The best known 'picture' is that of the cross on the highest point:
But strangely, this cross - suggesting a Christian link - is a bit misplaced: a missionary came to Birka in the 9th century to convert the Vikings. Although the Vikings were quite happy to add a God to their 'collection' (headed by Odin), they were not prepared to abandon the existing Gods and were never converted.
The Viking settlement on Birka suddenly disappeared in the 11th century and the great mystery is that no-one knows what happened to make it disappear. Lots of theories, but no clear direction.
During the day, the island is full of day trippers, on ferries or with own boats. At night, there were just 4 boats, including us.
During the night, the wind came up and we were rolling around a bit.
This morning we went South along the Södertalje canal and are now in a harbour called Skansholmen.
As it is blowing hard and expected to be similar for another day, we'll stay here tomorrow as well.