Two European countries now boast a longer list of UNESCO World Heritage sites with the addition of five historic Viking-age ring fortresses in Denmark and a planetarium in Friesland, the Netherlands.

© Stichting Werelderfgoed

The Netherlands welcomes its 12^th UNESCO World Heritage site: the Eise-Eisinga Planetarium in Franeker. Nominated to be a World Heritage site as early as 2003, this planetarium is the oldest functioning one in the world. Dutch amateur astronomer Eise Eisinga built a movable model of the solar system between 1774 and 1781, using a scale of 1:1,000,000; one millimeter to correspond to one thousand kilometers so that the model could actually fit in his living room.

© Stichting Werelderfgoed

Still in its original state, the planetarium is open to the public year-round. The Netherlands’ other popular UNESCO World Heritage sites include the Kinderdijk windmills, Beemster and Willemstad.

In Denmark, five Viking-age ring fortresses join the country’s UNESCO World Heritage list. Built between 958 and 987 under Danish Viking king Harald Bluetooth as defensive structures, these fortresses feature remarkable symmetry and remain some of the most prominent archaeological remains from the Viking Age in Denmark.

Borgring © VisitDenmark – Rune Hansen

In Aggersborg in Northern Jutland, the largest of the five ring fortresses sits near Løgstør. Built in the 980s, this 935-foot-wide fort features four gate openings, each pointing to a compass corner. The fortress also includes a tower in the center surrounded by 48 houses.

Another of these fortresses can be found in Fyrkat near Hobro in Northern Jutland, also built in the 980s, with impressive views from the rampart. Evidence suggests this fort was most likely built to maintain royal power, with a cemetery just north of the fortress indicating men, women and children lived here. Outside the fortress a reconstruction of one of the largest houses stands.

© VisitDenmark

The other three fortresses sit in Nonnebakken, Borgring and Trelleborg. The remains at Borgring remain an archaeological mystery, while visitors to Trelleborg can explore the lives of Vikings by visiting the reconstructed village of Slagløse.