In 1325, the Teutonic Knights built a castle called 'Yladia' or 'Ilaw', later known as 'Preussisch Eylau', in the center of the Old Prussian region Natangia. Ylow is the Old Prussian term for mud or swamp. The settlement nearby developed slowly, but in 1348 the Teutonic Order gave the privilege to establish twelve pubs at the surrounding area of the castle. Even though the village had only a few inhabitants, due to its central position it was often used as meeting place for different officials of the Order. In 1427 e.g. the Eylau County Law (Eylauer Landesordnung) was published by the Order.
Throughout the Thirteen Years' War the castle was besieged on May 24, 1455 by troops of the Prussian Confederation under the command of Remschel von Krixen, but the garrison defeated these troops. Also throughout the Horsemen's War in 1520 the castle was unsuccessfully besieged by troops of the Polish Kingdom, which caused a devastation of the village itself.
References:The church of the former Franciscan monastery was built probably between 1515 and 1520. It is located in the UNESCO World Heritage Site of Old Rauma. The church stands by the small stream of Raumanjoki (Rauma river).
The exact age of the Church of the Holy Cross is unknown, but it was built to serve as the monastery church of the Rauma Franciscan Friary. The monastery had been established in the early 15th century and a wooden church was built on this location around the year 1420.
The Church of the Holy Cross served the monastery until 1538, when it was abandoned for a hundred years as the Franciscan friary was disbanded in the Swedish Reformation. The church was re-established as a Lutheran church in 1640, when the nearby Church of the Holy Trinity was destroyed by fire.
The choir of the two-aisle grey granite church features medieval murals and frescoes. The white steeple of the church was built in 1816 and has served as a landmark for seafarers.