In 1586 Mikołaj Krzysztof "the Orphan" Radziwiłł ordered to townspeople to build a number of fortifications. Till the end of XVI th century the building was mostly finishes. The high earth wall was the main part of the fortification structures. It looked as a pentagon with 7 bastions and covered the city from all sides. It was possible to enter the city only through one of the five gates – Sluck, Klieck, Viĺnia, Mir and Castle gates. The city structures were surrounded by the water bank, linked with the Uša river. A bascule bridges were located in the front of each gates. There are also stone cloisters in the fortification system – Benedictine’s, Jesuit’s and friars minor order’s cloisters. They locked the direct road to castle. Periodically, if necessary, fortifications were repaired by hired teams of craftsmen. It was paid by the magistrate from the city taxes.
During the Russian–polish war 1654–1667 Niasvizh twice was taken by storm in 1654 and 1659. After the Northern war fortifications were renewed. After including of Niasvizh to the Russian empire fortifications have lost their value. Now preserved only some elements of fartificatons, such as Sluck Gate and the tower of the Castle gate.
The Town Sluck Gate
Town Sluck gate is a unique memorial of Belarusian baroque. It is the only one of five town gates built in the system of urban fortification at the end of the 16th – beginning of 17th centuries which have survived in Niasvizh and the whole of Belarus.
According to T. Makowski’s engraving of the beginning of the 17th century, originally Sluck (Kapyĺ) gate was a small tower with a four-sloped roof. It was separated from the dike with a lifting bridge. During thewarfare of 1654, 1660, the town fortification including the town gates were badly damaged. Under the Royal Privilege of October 29, 1669, they were rebuiltanew. In 1700 (due to some sources in 1760), Sluck gate was reconstructed in Baroque.
According to inventories, there was aboxroom for the guards and clerk who collected taxes. Everyone who entered the town had to paycustoms dues. It is indicated on the plate which has preserved in the gate wall to this day. There was Our Lady Chapel with an oak-carved altar on the first floor.
In the 70-s of the 20th century, repair works were carried out in Sluck gate: the façade and roof, oak doors, windows, staircase to the first floor, and balcony facing the town were restored.
In September 2007, a general overhaul of the town gate and beautification of itsadjacent territory were completed.
The Castle gate tower
The Castle gate tower is the most ancient stone construction in the town. Its architecture reflects the traits of Belarusian fortification in Gothic and Renaissance. The decorative solution of the defensive tower with loopholes is based on the contrast of red colour with whitened plane niches and trims. In old times, the tower fulfilled a defensive function. At present, it is the belfry of the Catholic Corpus Christi church.