The medieval Pärnu was actually two urban organisms, of which the right bank belonged to the Ösel–Wiek bishopric, and the left bank to the Teutonic Order. Although they both had harbors on the big trade route leading to Ruthenia, only the Teutonic Pärnu gained the status of a full member of the German Hanseatic League and developed into one of the most important medieval cities of Livonia. In 1263, the invasion of pagan Lithuanians destroyed the right-bank Pärnu, and the bishops moved to the north Haapsalu. Livonian land master Konrad von Mandern take advantage of this situation and ordered in 1265 to erect on the left bank of the river a powerful conventual castle, which was the seat of the commandry. At the beginning of the fourteenth century, the city plan of New Pärnu was also formed, which was surrounded by the perimeter of the stone walls, integrated with the Teutonic castle.
Over the next decades, misfortunes evaded both cities of Pärnu and the castle. It was not until 1473 that not fortificated Old Pärnu was looted by Baltic pirates. In 1560, the commander Rutger Wolf gave the castle and the city to the representatives of Lithuania, however, Pärnu did not defend itself against the forces of Ivan the Terrible, which in 1578 took the city and the castle for four years. After regaining in 1582 by Polish–Lithuanian Commonwealth, it became the capital of the Polish province. One of the most important decisions of the Polish authorities was to liquidate the Old Pärnu and resettle all inhabitants to the left bank of the river.
During the Livonian War and then the Polish-Swedish war, the castle was destroyed. In 1617, the city was taken over by the Swedes, whose rule lasted until 1710, when the Russians took control, ruling until proclaiming independence by Estonia in 1918.
The Teutonic Castle in Pärnu was a typical, square conventual complex with the most important monastery rooms located on the first floor, around a stone cloister connected to them from at least three sides (eastern, western and southern). The castle also had at least one tower, located in the north – east corner of the upper castle. The stronghold was surrounded by two lines of defensive walls equipped with corner towers. The first walls circuit separated the zwinger, surrounding upper castle area, and the second set a large outer bailey.
The defensive walls of the city extended east of the castle and were connected with it. The north and east curtains ran straight, the south had two small bends. A number of gates led to the city: the northern River, Water and Guild, eastern Cattle Gate and south Riga and the Holy Spirit Gate. The north-eastern and south-eastern corners were strengthened by the cylindrical towers, the latter of which is the Red Tower preserved to this day. Originally, it was four-storey, and the thickness of its walls reached 2-3 meters. In addition, the walls had several semi-cylindrical towers.
The teutonic castle did not survive in the slightest way to modern times. The only preserved fragment of city fortifications is a tower between the houses from the first half of the 14th century, known as the Red Tower or the Prison Tower. Currently, it is one level lower than the original appearance.
Borowski T, Miasta, zamki i klasztory, Inflanty, Warszawa 2010.