The importance of Coria in Roman times is reflected in its defensive military fortification erected during the Early Roman Empire (1st century). Its layout is the shape of an irregular trapezoid featuring solid walls of granite ashlar masonry, completed with the traditional pattern of stretcher and header bond on their faces and the internal reinforcement with a 3-metres-thick layer of concrete. These walls are defended by twenty-three robust square or cube-shaped towers, each located about 20 or 30 metres apart, surrounding its total perimeter of 1,065 metres. The imposing fortification extends across six hectares of land, as the walls adapt to the uneven terrain with their width occasionally exceeding 4 metres and their height ranging between 10 and 14 metres.
These enormous defensive walls protect its boundaries and give access through four entrance gates: to the north, the Puerta de San Pedro/Puerta del Sol (1st century); to the southwest, the Puerta de la Guía/Puerta de la Ciudad (1st century); to the northwest, the Puerta de San Francisco/Puerta del Rollo (16th century); and to the east, the Puerta del Carmen/Puerta Nueva (16th century). These huge gates are reminiscent of the Roman domination and presence in the territory. Although, throughout its extensive history, this borderland has been subjected to alterations and several episodes of war, the Roman City Walls of Coria, as a whole, are arguably among Europe’s best-preserved fortifications.
Visby Cathedral (also known as St. Mary’s Church) is the only survived medieval church in Visby. It was originally built for German merchants and inaugurated in 1225. Around the year 1350 the church was enlarged and converted into a basilica. The two-storey magazine was also added then above the nave as a warehouse for merchants.
Following the Reformation, the church was transformed into a parish church for the town of Visby. All other churches were abandoned. Shortly after the Reformation, in 1572, Gotland was made into its own Diocese, and the church designated its cathedral.
There is not much left of the original interior. The font is made of local red marble in the 13th century. The pulpit was made in Lübeck in 1684. There are 400 graves under the church floor.