Saaremaa Island was conquered by the Crusaders in 1227, but in the following years numerous pagan uprisings broke out. It was not until five years after the uprising of 1260, that the Teutonic Order began the construction of the first fortifications in place of the later castle. It received its final architectural form only in the years 1330-1360. The castle was not the seat of a teutonic convent, but the property of the bishop. The end of its medieval history followed the fall and secularization of the Ösel–Wiek bishopric in the second half of the 16th century. The Livonian War, which caused enormous damage to the continental part of Estonia, did not fortunately affect fortress, which along with the island was sold to Denmark. In 1645, the Danes were replaced by the Swedes, and after 1710 the castle belonged to the Russians. Throughout this period, up to the beginning of the 19th century, Arensburg as the capital of the island and region, kept its military significance, and its fortifications were modernized. Fortunately, these extensions did not involve dismantling older, medieval fortifications. The first conservation work was carried out in 1904-1912, and a large-scale renovation took place in 1968-1985.
The oldest castle consisted of a single line of walls reinforced with a single, main tower. At the end of the fourteenth century, the stronghold was already a fully developed conventual castle, consisting of a regular, square courtyard to which four wings of buildings were adjacent. In one corner of the fortress stood the Sturwalt Tower, in the second slimmer and taller Long Hermann Tower. The north-eastern tower was interestingly solved, which as the last point of defense was separated by a free space, where a sewage from latrines placed next to guest rooms was probably flowing.
Following the example of other Teutonic castles, the most important rooms were located on the first floor, and communication between them was provided by a stone cloister, built-up due to low temperatures. The entire west wing was occupied by the bishop’s rooms, the majority of the southern wing by large representative refectory, and the eastern wing by dormitory and the smaller refectory. The castle did not have a chapter house, the councils might have been held in the northern refectory at the round table. An unusual architectural solution was the bishop alcove placed in the west wing, surrounded by an extremely thick wall and windowless, probable place of final shelter. The utility rooms were on the ground floor, the third storey had defensive functions.
The main building of the castle was surrounded by a hydrated moat, along which a small outer wall ran from the inside, giving the area of zwinger. Around the moat there was an outer bailey, also surrounded by a moat and fortifications. Originally it was a wooden – earth fortifications, which was replaced at the turn of the 14th and 15th century by a stone wall of 687 meters long. The last medieval extensions took place in the mid-fifteenth century, when the external wall was raised and equipped with towers.
Arensburg is the best preserved medieval castle of the entire east coast of the Baltic Sea. Despite the damages and modern reconstructions of the north-western tower and vaults of the cloisters, the basic shape and most of the castle rooms, along with the gothic vaults and numerous architectural details, have survived. In the castle there is the Saaremaa museum, and the spacious area in front of the monument is the place of various outdoor events.
Borowski T, Miasta, zamki i klasztory, Inflanty, Warszawa 2010.