Färjestaden - Gråborg

8km/5mi northeast of Färjestaden is the Gråborg, the largest refuge fort on the island, which was probably constructed during the great migrations and remained in use into the Middle Ages. Its ramparts, up to 6m/20ft high, enclose an elliptical area 220m/240yd long by 165m/180yd across. There are remains of an impressive vaulted gateway. Near the Gråborg are the ruins of St Knut's Chapel (13th C.).