Adelsö is a small island in the middle of the lake Målaren several tens of kilometers to the West of Stockholm city. Perhaps unremarkable on a map, Adelsö is probably better known as the island near to the viking tourist attraction at the old Birka settlement, on Björkö (lit. Birch) island.
Adelsö itself is host to human habitation since the Stone Age, and best known for the ruins of Alsnö Hus at Hovgården. The Hovgården area also has several burial mounds for royalty and nobility, though at present they would have been easily overlooked as oddly positioned hills were it not for the heritage signage. Alsnö Hus itself was a stone summer residencestructure rebuilt by King Magnus III, and burned down in an uprising. it is now a ruin, though its footprint is clear enough if one examines the ground.
The Hovgården site overlooks the historical economic powerhouse, Birka, and is itself heavy with weight of history. Incidentally, it is also a UNESCO World Heritage Site. Also not to be missed in the area are the remarkably well preserved Hacon Stone runestone and the nearly millennium old Adelsö church. For those who visit, I would recommend taking the bus line 312, which goes around the island and takes ride on a rather remarkable cable ferry right across the lake.