This was a Fortress build in medievil times by the water front in Mällaren,the lake that surrounds Stockholm.
One had to pass this part of the countryside to get Birka and Uppsala,two prominent cities the later being one of the most important in Swedidh history.

During this excavation we studied the castle it self along with its surroundings and harbour.

Many artifacts were found,even though the castle itself had been burnt to the ground and emptied of all its content.

About 15 meters into the water the lays a shipwreck,a cogg of about 20 meters in lenght.
This was used to transport items such as food and the likes.

Many pieces of arms were found,such as spears and a sword. Along with horseshoes and nails used in ship building.
One of the most surprising founds was a man's shoe,that against all odds had survived the conditions of the landskape.

For further info on ths you may drop me a line and I will be able to give you a list of bookd and articles on the subject.