In 1645 the Swedes took it by storm, and their possession of it was confirmed by the peace of Roskilde in 1658; but the sympathies of the people were with Denmark, and a popular insurrection succeeded in expelling the Swedish forces, the island coming finally into the possession of Denmark in 1660.
The differences between the two states were finally adjusted by the peace of Copenhagen (May 27, 1660), Denmark ceding the three Scanian provinces to Sweden but receiving back the Norwegian province of Trondhjem and the isle of Bornholm which she had surrendered by the peace of Roskilde two years previously.
The Danish king Hrothgar and his brother Halga, the sons of Healfdene, appear in the Historia Danica of Saxo as Roe (the founder of Roskilde) and Helgo, the sons of Haldanus.
The coast is indented by numerous deep bays and fjords; the Ise Fjord in the north, with its branches the Roskilde Fjord on the east and the Lamme Fjord on the west, penetrates inland for about 25 m.
The only other town of importance is the old cathedral city of Roskilde on the fjord of that name.