Gråborg is the largest ancient castle in Öland. It was built probably in the 6th century and enlarged through Middle Ages. According old tax reports dating back to the year 1450, Gråborg was owned by Vadstena abbey and functioned as a some kind of trade center. It was used for defence against Danish even in 1677. According to legend Gråborg was strongly associated with king Burislev Sverkersson who had grown up there with his half-sister Sofia of Minsk.
Gråborg Castle consisted of a circular wall, about 4-7 meter tall. There were three entrances and one of them was vaulted in the Middle Ages. Archaeological excavations have revealed lot of findings, which are stored today in Kalmar Museum.
There are medieval ruins of the chapel of St. Knut on the north side of castle.References:
Roman Walls of Lugo are an exceptional architectural, archaeological and constructive legacy of Roman engineering, dating from the 3rd and 4th centuries AD. The Walls are built of internal and external stone facings of slate with some granite, with a core filling of a conglomerate of slate slabs and worked stone pieces from Roman buildings, interlocked with lime mortar.
Their total length of 2117 m in the shape of an oblong rectangle occupies an area of 1.68 ha. Their height varies between 8 and 10 m, with a width of 4.2 m, reaching 7 m in some specific points. The walls still contain 85 external towers, 10 gates (five of which are original and five that were opened in modern times), four staircases and two ramps providing access to the walkway along the top of the walls, one of which is internal and the other external. Each tower contained access stairs leading from the intervallum to the wall walk of town wall, of which a total of 21 have been discovered to date.
The defences of Lugo are the most complete and best preserved example of Roman military architecture in the Western Roman Empire.
Despite the renovation work carried out, the walls conserve their original layout and the construction features associated with their defensive purpose, with walls, battlements, towers, fortifications, both modern and original gates and stairways, and a moat.
Since they were built, the walls have defined the layout and growth of the city, which was declared a Historical-Artistic Ensemble in 1973, forming a part of it and becoming an emblematic structure that can be freely accessed to walk along. The local inhabitants and visitors alike have used them as an area for enjoyment and as a part of urban life for centuries.
The fortifications were added to UNESCO"s World Heritage List in late 2000 and are a popular tourist attraction.