Radzyn Chelminski was the seat of the Teutonic Knights' Commandry. The castle is one of the oldest castles built by the Teutonic Knights, built in the 13th century. In 1446 the castle went into Polish control, in 1628 during wars with the Swedes the castle was partially devastated, slowly turning into a ruin.
Currently you are still able to see the tower - damaged by artillery fire. In 1780 Prussian authorities ordered to deconstruct whatever is let of the castle. Bricks from the three wings of the castle were used to build houses for the nearby community. The castle's deconstruction was stopped towards the end of the 19th century.
References:The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.