Krasnoarmeyskaya St. 9, Mir, Belarus
The first wooden Catholic church in Mir was built by the Ilyinich family at the beginning of the 16th century. Later, Mir came under the ownership of the princely Radziwiłł family, who constructed a new wooden Church of St. Nicholas, consecrated on October 18, 1587, by the Vilnius bishop Yuri (Jerzy) Radziwiłł, who later received the title of cardinal (the first in Lithuania). In 1599, Prince Nicholas Christopher Radziwiłł the Orphan began the construction of a stone church. The construction was completed in 1605, and the consecration took place on August 21, 1605. The church’s design is attributed to the Italian architect Bernardoni. During the laying of the foundation, the remains of a "pre-flood beast" (possibly a mammoth) were found in the ground. According to tradition, its bones were displayed in the church for a long time. This event was mentioned by Adam Mickiewicz in his poem "Pan Tadeusz": “Thus, in the Mir church, the priest hung the bones of pre-flood giants near the organ.”
Between 1604 and 1609, a two-story parish house (presbytery) was built next to the church. Over time, the church was not rebuilt and has come down to us in its original form. Repairs were carried out only twice: in 1710 by Prince Karol Stanisław Radziwiłł and in 1845 with the help of the Minsk prelate priest Franciszek Nowicki.

After the Polish uprising of 1863, the Tsarist government closed many Catholic churches in the territory of modern Belarus and transferred their buildings to the Orthodox Church. On October 7, 1865, the Church of St. Nicholas was re-consecrated as an Orthodox church. In 1876, the wooden roof was replaced with an iron one.
As of 1879, the church had two iconostases. The church housed vestments for clergy, a silver liturgical set of vessels, and liturgical Gospels. The bell tower had six bells, the largest of which (the one ordered in honor of the victory over the Swedes) was cast by order of the 8-year-old Prince Radziwiłł Rybónka in 1710 (his name was inscribed on the bell). Among the locals, the expression “Rave, like the Mir bell” was long in use. During World War I, the bell was sent for melting down by order of the Tsarist authorities.
In 1879, the St. Nicholas parish included several villages besides the town of Mir. On holidays, the church was visited by up to 600 people. Church records of that time note that the parishioners were very diligent and God-fearing: they avoided drunkenness, observed fasts, were friendly, hardworking, careful with regard to the church, and literate (60% of the parishioners in the town itself could read and write).
The two upper tiers of the main tower were lost during the conversion of the church into an Orthodox church in 1865 (according to other sources — after World War II). Previously, the tower was crowned with a sloping four-sided tent roof of the “cap” type, characteristic of castle architecture.

After reconstruction, the tower’s top looked different: in the second half of the 19th century, it had a “cuboid” tented roof, and during the Polish period in the 1920s — a pointed tent roof with a break. Currently, the tower is covered with a four-sided tent roof in the style of the towers of Mir Castle. Photo of the church at the beginning of the 20th century (before the Polish period):
In 1919, thanks to the efforts of priest Anatoly Matskevich, the church was returned to the Catholics. In 1937, a book by Alexander Snezhko titled "The Parish Church in Mir" was published in Lida, which remains the most comprehensive work on the history of the church to this day.
In the autumn of 1942, the parish priest Anatoly Matskevich was killed. Since 1946, the church was closed. During the post-war period, the two upper tiers of the towers and two side round turrets were destroyed, and the roof collapsed.
In 1990, the church was returned to the faithful, and restoration work began in 2001. In 2009, for the first time since the Great Patriotic War, priest Alexander Sevastyanovich was appointed as the church’s rector. Today, the Mir parish is the smallest parish in the Grodno diocese.
The Church of St. Nicholas is a three-nave basilica without a transept. The central nave is covered with a cylindrical vault with lunettes, the side naves with cross vaults. The central nave with a semicircular presbytery ends on the facade side with a massive, square in plan, four-tier tower with a tent roof. The side naves on the main facade are finished with round towers in plan with spiral staircases; on the altar side — with rounded sacristies in plan. The side facades, devoid of decoration, are pierced by tall window openings with semicircular tops.
Under the presbytery was a spacious vaulted crypt, which contained about 30 burials; in 1866 the crypt was sealed.
Sources:
https://www.limberi.by/ekskursii/attractions-belarus/kostel-sv.-nikolaya-v-mire.html
https://ru.wikipedia.org/wiki/Николаевский_костёл_(Мир)