Bornholm's many historic castles, trenches and fortifications bear many testimony to the island's long history. Today they are popular attractions on the island. Due to its central location on the Baltic Sea, Bornholm has been an arena of fighting and looting many times.
In addition to the ruins of Hammershus Castle, there are Lilleborg & Gamleborg in the Almindingen forest, Gamleborg in Paradisbakkerne, Rispebjerg ramparts, Christiansø fortress island, fortifications in Rønne, Storeborg walls near Rø, Borgvolden ramparts on the Rø plantation, and many other small ramparts and fortifications around the island. Bornholm's round churches were also small castles that served to protect the population.
Hammershus is Bornholm's most impressive medieval castle ruins and a popular excursion destination. Right on the road from Vang to Sandvig, Hammershus offers its visitors impressive views. In the 12th century, the construction of a fortress began here. Over the centuries, it has transformed into an almost unique fortress, surrounded on three sides by steep rock walls. The castle was the headquarters of church dignitaries until the occupation of Bornholm by the Lubeks in 1522. In 1658, Bornholm and the castle with it became Swedish territory. This was a short period, and year later the Danes ruled Hammershus again. The castle experienced its heyday in the 16th century.
From 1743, no ruler lived in the castle anymore, which caused the building to collapse, which could only be stopped in 1822, when it was placed under protection. The facility is currently being completely renovated.
The walls in Rispebjerg is Bornholm's oldest fortress, east of Pedersker, on the Øle Å River, where rituals were held at the site back in the Stone Age. It is believed to be the temple of the sun. In the Iron Age, around 100-300 AD the temple became a fortification to protect the local population against attacks by robbers. It was a rampart with a palisade fence, turrets and a pavement. The whole thing was surrounded by a moat. On the one hand, the entire complex was protected by the river.
Today, unfortunately, there is not much to look at as all the wooden fixings are long rotten. The ramparts are still clearly visible. Additionally, the location and size of the buildings have been marked in several places.
The remains of Gamleborg Castle are in the Almindingen forest area. This castle was the first massive castle complex on Bornholm, built at the time of the Great Migration around 750 AD, as a refuge for people from other Viking tribes, Gamleborg experienced its peak before Lilleborg during the Viking Age between 800 and 1100 AD. At that time, it was the main fortress of the island and the headquarters of the king. The facility measures 264 x 110 m.
Around 1100 AD the castle was heavily fortified again before being abandoned in favor of the new Lilleborg Castle which was built just 700 meters away. The reason for this decision is unknown. The area of Almindingen was not yet forested at that time. Rather, it was a less wooded, hilly area with moors and lakes, valleys and boulders. Due to its wealth, Bornholm was often visited by foreign troops. People also looked for protection in the event of natural disasters.
Today, still can be seen a few remains of the foundation walls. The earthen wall is located on the northern, western and southern edges of the former castle. The east side, on the other hand, is very steep and offers good protection against attackers. The great north gate is still clearly visible. In the first period of the castle's creation, there was also a southern gate here, which was later closed and replaced with a gate from the south-west. Since almost no archaeological finds have been discovered at the complex, it is assumed that it was used in case of attacks. Apparently, the castle was not inhabited all the time.
Lilleborg (Little Castle) replaced Gamleborg as a royal fortress on Bornholm in the 12th century. However, the size of both systems was difficult to compare. Nevertheless, Lilleborg was also a defensive fortress. In the early Middle Ages, it served the king as the center of secular power on Bornholm, and thus was an alternative to Hammershus Castle and the church that was the archbishop's stronghold in the north of the island.
Archaeological finds of coins from the times of Knut Magnusson (1146-57) and his successor Valdemar I (1157-82) testify to the age of the castle. It is also assumed that one of them must have stayed in the castle. In 1259, after it was captured by King Archbishop Jakob Erlandsen, it was destroyed by an attack with the support of Prince Jaromar from the island of Rügen. This was the result of a constant struggle between the church and the king on the island. During the excavations, apart from weapons and traces of fires, other coins were also found, which suggests that the object must have been inhabited later. So it looks like it wasn't completely destroyed, but it gradually deteriorated over the years.
Borgesøen is a lake in the immediate vicinity of the remains of the fortress. At that time, it served as part of a defense system, then covering the entire 16-meter hill. The only passage was a wooden bridge. On the ring wall of the entrance to the castle, a corner tower measuring 9.5 x 9.5 m was guarded. From that moment on, you could fight enemies from all sides. The castle walls were 2.40 meters thick. Further walls led down to the lake and were likely built to secure the water supply as the castle had no wells.
Today, the remains of the castle, which are located on the hill, are easily accessible from the road from Ronne to Svaneke, these are the foundation walls that once surrounded the top of the hill for 76 m.
Paradisbakkerne is a forested area of hills in the east of Bornholm. A very varied landscape and interesting area includes gorges, rocking stones, moors and lakes, and the ruins of an old castle. The protective castle, also known as Gamleborg, dates from around 400 AD when different peoples and tribes wandered around Europe in search of new lands. As a result of this migration of peoples, there were also clashes between the local people and foreigners. Gamleborg was built to protect the people of Bornholm. The object, located on a 14-meter high rock, was difficult to access. Based on archaeological findings, it is assumed that the castle was built around 800 AD.
Today, you can still find some stone walls and foundations.
Round churches on Bornholm are probably the most interesting fortifications on the island. In addition to being places of worship, they were also a refuge for the people of Bornholm during attacks. Almost at the same time, in the mid-12th century, four round churches were built equally across the island. Churches have never been built directly on the coast and always in strategically cleverly chosen locations such as small fortresses. The circular church building had a flat roof with a circular run. So the defenders could use the church as an observation point and defend it well. The church itself only had very small and narrow windows. The entrances to the upper floors were easy to defend.
Today, Bornholm's round churches have pointed conical roofs. There are four round churches in Østerlars, Olsker, Nyker and Nylars.
At the end of the 18th century, in times of constant struggle on the Baltic Sea region, the Danish king Frederik V decided to expand the city of Rønne into a fortress. A seaport was planned to protect the Danish fleet from Swedish attacks and a fortress-like curtain wall surrounding the entire city. Ambitious construction work began in 1687, but the project was never fully completed as construction was stopped in 1789. By that time, Rønne had built various moats and a shooting tower to the south of the city. The tower (Kastellet) looks very similar to Bornholm's round churches as it is whitewashed. An identical example is Lille Tårn on the pea islands - Ertholmene.
The fort was equipped with 10 large cannons on the top floor and served as a powder magazine. In addition, various other buildings were built in 1816, which are surrounded by a large wall, and now it is home to the Bornholm Defense Museum.
The ramparts on Bornholm were used to defend the natural harbors to prevent enemy troops from landing on the island. They can be found spread over the entire coastline, for example in Arnager Bay in Bølshavn, Gulhals Batteri and Malkeværnskansen between Årsdale and Nexø, Hasle - Helligpeder Skanse, Kanondalen Rønne (Rønne Fortress), Langeskanse near Balki, Sandvig Batteri, Sveose Odde, Sveose Odde Skanser and St. Myregård (Arnager). Not all ramparts were built at the same time. Some date back to the 15th and 16th centuries.
The Svaneke Skansen building right next to the smokehouse in Svaneke is especially worth seeing. It was built to protect the port agains foreign ships. Originally, there were North and East batteries north of the port, as well as a watch battery and two more batteries south of Svaneke port. At the turn of the 18th and 19th centuries, 11 guns were stationed there. English warships in particular were fired upon at that time.
Dueodde's cannon battery plays a special role among the fortifications of Bornholm. This is not a defensive installation like all the others, but a German artillery position with bunkers that were built by the German Wehrmacht in the south of Bornholm in 1942 during World War II. From there, the German occupiers wanted to control all ship movements on Baltic Sea.
As planned, the huge facility was never completed and has never seen any cannons. Nevertheless, you can see huge bunkers in the Dueodde pine forest.
Bornholm's medieval center is an amusement park with no specific historical reference. Nonetheless, it offers an unparalleled insight into life on Bornholm between the 11th and 13th centuries, as well as the architecture of a medieval fortress. All buildings are based on historical models.
In addition to a medieval village with stables, houses, a blacksmith's shop and other workshops, there is also a wooden defensive castle, comparable to the one on Rispebjerg, with a tower, other buildings and a circular track on the fence. Impressive shooting shows are especially popular with young and old.
Christiansø Fortress is not on Bornholm, but on the Pea Islands to the east. Ertholmene, as they are called in Danish, can only be reached via Bornholm. Christiansø's fortifications are very worth seeing as the whole island has been covered by fortifications. The fortress on Christiansø dates back to 1684, when Danish King Christian V decided to extend the natural harbor of the archipelago.
The defense towers, walls and ramparts were erected in a very short time under the supervision of the Norwegian engineer Anthon Coucheron and 450 employees. The fortress passed its test in 1808, when English warships attacked a military port to sink Danish corsairs. The attempt of attack was unsuccessful. In addition to serving as a harbor and fortress, the Pea Islands also served as a prison island due to their isolated location. Many famous prisoners have been imprisoned on barren rocky islands.
Today you can go on full-day excursions from Bornholm to the Pea Islands and visit the well-preserved fortifications.