The 'Vauban Fortress' of Foras was initially a strategic fortification established by Philip the Fair, circa 1300. The donjon was rebuilt in 1480-1490 by Jehan II de Brosse.
The creation of the Rochefort Dockyard in 1666 made it a centrepiece of the system for defending the approaches of the Charente, which is prohibited from entering. At the end of the 17th century, François Ferry, the engineer of King Louis XIV, transformed the old feudal residence into the fort. In 1689, Ferry reinforced the walls of the Donjon to set up a battery of 9 canons and a signaling point. In 1693 a lower circular battery was set up to control access to the river Charente. The donjon received a signal station from 1889 to World War II.
Today classified as a Historical Monument, the castle houses a museum of regional history. Free entrance or guided tour of the fortification and the underground parts of the keep at 2 p.m every day (except Monday) between June 1st and the third weekend of September.
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.