The first permanent inhabitation in Ertholmene, generally called Christiansø, was the result of the Danish-Swedish conflicts in the late 17th century. As Denmark needed a naval base in the central Baltic Sea, a fort was built on Christiansø and Frederiksø in 1684 which served as an outpost for the Danish Navy until 1855. The islands' external appearance has changed very little in over 300 years. Girdled by thick granite walls with old cannons pointed seaward, Christiansø is a picturesque tourist spot seemingly frozen in time. A former part of the fort, Store Tårn has housed the Christiansø Lighthouse for the past 200 years, and a small round tower on Frederiksø, Lille Tårn, serves as a museum.
References:The Château de Foix dominates the town of Foix. An important tourist site, it is known as a centre of the Cathars. Built on an older 7th-century fortification, the castle is known from 987. In 1002, it was mentioned in the will of Roger I, Count of Carcassonne, who bequeathed the fortress to his youngest child, Bernard. In effect, the family ruling over the region were installed here which allowed them to control access to the upper Ariège valley and to keep surveillance from this strategic point over the lower land, protected behind impregnable walls.
In 1034, the castle became capital of the County of Foix and played a decisive role in medieval military history. During the two following centuries, the castle was home to Counts with shining personalities who became the soul of the Occitan resistance during the crusade against the Albigensians.