For more than four centuries (1513-1939), Nesvizh's history was inextricably linked with the activities of the Radziwill princely family, who built their main residence next to the town in the late 16th century. In 2005, the magnificent castle complex was added to the prestigious UNESCO World Heritage List. After extensive restoration, it was ceremonially opened to tourists in July 2012 and today is one of the most valuable monuments of Belarus, attracting hundreds of thousands of tourists every year.

Niasvizh as the seat of the Radziwill family
The first confirmed historical data about Niasvizh date back to the mid-15th century and are connected with the person of Mikolaj Jan Nemirovich. The year 1446, when he received the Niasvizh estate from the hands of Casimir IV Jagiellon, in gratitude for his political support, is considered to be the founding date of the town. It came into the Radziwill family's possession through the Lithuanian Kishkas family. In 1513, Nesvizh's owner Anna Kiszczanka married Jan Radziwiłł, and in 1533, the estate was inherited by their sons: Mikolaj, known as Czarny, and Jan. It was Mikolaj "Czarny" Radziwill who, in 1547, was the first to adopt the title of "Prince at Ołyka and Niasvizh", emphasising the high rank of the resort.

The centre of the Radziwill estate became Nesvizh thanks to the eldest of Mikolaj "the Black"'s sons, Mikolaj Krzysztof "the Orphan". After the establishment of the Nesvizh Ordinance (1579) and the approval of the Magdeburg Law for the town (1586), the construction of a magnificent fortified residence was to seal Nesvizh's rank. As early as 1582, in the vicinity of the extensive wooden defensive manor house which had previously existed here, the foundations of the castle were begun. In addition, thanks to the foundation of Radziwill "the Orphan", Niasvizh gained an urban layout with a regular grid of streets and quarters, a number of secular and sacred buildings and fortifications.

Description of Niasvizh Castle
. Around 1600 the main part of the castle layout, located on a promontory between two artificial lakes on the Usha River, was already completed. Work was still underway on the entrance gate with a tower, which can be seen in its full glory in an engraving from 1604. The designer of the complex is believed to have been the Jesuit architect Giovanni Maria Bernardoni - responsible for the urban design of Nesvizh and for most of the princely foundations there. Currently, however, researchers only speak of Bernardoni's involvement, who, significantly, did not arrive in Niasvizh until 1586, at certain stages of the building's construction.

The castle's defences, although already guaranteed by its very location, were strengthened by modern fortifications. The quadrilateral foundation was surrounded by earth ramparts with powerful corner bastions and a deep moat. A long wooden bridge led to the fortress, which could be quickly dismantled in case of danger. The area could be accessed through a brick gate with a clock tower superstructed on the inside. Immediately opposite the gate was the Radziwiłł palace, and next to it a tenement house with a tower and an arsenal. These three most important buildings separated the courtyard, in the middle of which a well has been preserved to this day. The main palace building is distinguished by a chiselled front loggia and a gabled, curved roof. In addition, there was an armoury, barracks, prison and outbuildings within the castle walls. According to the 1658 inventory, the castle's rooms, which included 12 ceremonial halls, were richly decorated with sculptures and paintings and decorated with marble, stucco and gilding.

Destruction and Reconstruction of Nesvizh Castle
The first major changes to the appearance of Nesvizh Castle were made by Alexander Louis Radziwill, who, in the mid-17th century, built a gallery connecting the palace with the castle house. Soon afterwards, as a result of a siege by Russian troops, the castle was severely damaged. The roofs, the helmet of the castle tower and the second-floor flats in the palace and tenement were destroyed. During the Third Northern War, the Swedish army destroyed (1706) the castle fortifications and looted its furnishings. Reconstruction work carried out in the 1820s removed the damage and extended the castle, whose defensive function has since lost its importance.

The princely residence became primarily a centre of cultural life, with a theatre hall, a chapel, an extensive book collection and a collection of paintings, weapons, coins and medals. During the time of the Bar Confederation, the castle was first seized by the Russians, and a significant part of the Radziwiłłs' archival and artistic collection was taken away and dispersed. The castle underwent thorough restoration in the 1880s. An extensive English-style landscape park was then created in its vicinity. In the interwar period, Nesvizh Castle witnessed an important meeting between Józef Piłsudski and Polish aristocrats. Finally lost by the Radziwiłłs in 1939, after World War II it was transformed into a sanatorium, which operated here until 2001. This function of the building led to significant transformations in the layout of the rooms and the destruction of the castle's interior furnishings.

Controversial renovation and the present appearance of the castle
. The present appearance of Nesvizh Castle is the result of a comprehensive, multi-year renovation carried out until 2012. Numerous controversies have been associated with these works due to their incompatibility with the current conservation doctrine and their leading to a significant loss of authentic historic substance. Criticism was levelled not only in Belarus, but also internationally, for, among other things, the complete demolition and subsequent reconstruction of the castle's eastern wing and the reconstruction of the tower's finial in the style of an Orthodox dome, which did not fit in with the overall complex (after criticism in 2012, the tower's original cupola was restored). Nevertheless, as a result of these measures, the castle was lifted from ruin and turned into a major tourist attraction in Belarus.

At present, Nesvizh Castle functions as a museum that - in addition to visiting the restored historic interiors - offers concerts, temporary exhibitions and theatre performances to tourists. The inclusion on the UNESCO World Heritage List underlines the historical value of the ensemble, which, in addition to the castle, also includes the Corpus Christi Church - the burial place of the Radziwills - and the park.