One of the oldest towns in Volhynia is Zaslavl. It was owned in turn by the Ostrogski, Zaslavski and Sanguszko families. They all cared for the town and its development, seeking various royal privileges for it. Thanks to its last owners, Zaslavl became an important trade and artistic centre. An important centre was the missionary church complex, which united the old Zaslavskiy palace with the new Sanguszko residence and garden complex. They were created by an Italian architect (church and monastery), Polish sculptors (church interior) and a Warsaw gardener.

Zaslavl - the city of the Ostrogski and Zaslavl families
. Zaslavl is one of the oldest towns in Volhynia, picturesquely situated on the Horyn River. It dates back to the 12th century, although it was not granted town status until 1583. It was founded on the lofty left bank of the Horyn River and was one of the most important seats of the Ostrogski dukes from the very beginning. As late as the mid-15th century, Jurij Ostrogski built a fortified castle in Zaslavl. After the Ostrogski family died out, their estates (including the Ostrog Ordinance) passed to the Zaslavskys, who took their family name from Zaslavl, and then it passed to the Sanguszkos. Successive owners took care of Zaslavl, seeking various royal privileges for the town and taking care of its urban development.

Zaslavl - urban development
A synagogue was built in the 16th century. In 1599 Prince Janusz Zaslavski issued a foundation charter for the Roman Catholic parish of St John the Baptist and built a monumental temple on the plan of a Latin cross with a square, high tower in the façade. Zaslavski founded a school and hospital at the parish, as well as a vicarage.

One of his main ideas was to create an ancestral mausoleum at the temple. Aleksander Zasławski, son of Janusz, donated 6,000 Polish zlotys in his will for this purpose. The Zaslawski family burial chapel was finally built next to the church in the 1730s.

Prince Janusz Zaslavski also funded a Bernardine outpost, initially giving them use of an Orthodox chapel and donating a painting of the Virgin Mary, which later became famous for its numerous miracles. The complex of a masonry church on the ground plan of a Latin cross and a monastery was built by 1630, possibly to a design by Jacob Madlain and the Bernardine friar Bernard Avelides. In the 17th and especially in the 18th century, the church became a very flourishing Marian shrine with a miraculous image of Our Lady of Zaslavl. Since the Soviet era, the church and monastery have continuously served as a maximum security prison.

Initially, the Zaslavlskis resided in a castle on the Horyn River embankment, near the Transfiguration (Preobrazhenskaya) church, the parish church and the Bernardine temple. Janusz Zaslavski, however, built a new residence on the other side of the river, which became the nucleus of the later new Zaslavl.

Zaslavl's development and splendour came to an end in the 17th century with the invasion of Bohdan Khmelnytsky, who sacked, burnt to the ground and occupied the town in 1648.

Zaslavl - the city of the Sanguszko family
. In 1720, the Zaslavl estate was inherited from her brother Alexander by Marianna Lubomirska, who was the second wife of Pavel Karol Sanguszko. From this time, a new economic and artistic chapter opened in Zaslavl's history. Paweł Karol, initially a mediocre magnate in terms of wealth, became one of the richest people in the Republic in the 1820s and 1830s through three successive marriages. In particular, Marianna Lubomirska brought considerable lands to Sanguszko as dowry, with the Ostrog Ordinance at the forefront.

Paweł Karol Sanguszko took care of the main centres of his vast estates, granting Zasław numerous trade and craft privileges. Thanks to these, the town, which had fallen into decline after the Cossack wars, became once again in the mid-18th century not only an important centre of trade, but also an artistic centre centred around Sanguszko and his third wife Barbara, née Dunin, who both showed great patronage ambitions and was a dashing and good administrator.

Paweł Karol Sanguszko rebuilt the ruined Zasławski Palace by 1745. He did not enjoy his residence for long, however, as he died in 1750. His widow, Barbara of the Dunin Sanguszko family, began construction of a new residence in 1754. The foundress consulted the plans of the new residence with the architect Jakub Fontana in Warsaw, and personally supervised the progress of the work. In 1759 the roof was covered with tiles, and between 1759 and 1764 a representative courtyard surrounded by outbuildings and gates was designed between the old Zasławski Palace and the newly built one. The plans for the extensive palace garden were created by the Warsaw gardener Carl Georg Knackfuss.

New Zaslavl and the Missionary Church
. After taking possession of Zaslavl, Pavel Karol Sangushko not only invested in the renovation of the parish church and the old Zaslavl Palace, but also consistently and consciously sought to develop the new part of the town situated on the right bank of the Horyn River. To this end, he issued economic privileges and applied to the king for a charter for Nový Zaslavl (1754). Its central part was the castle erected by Duke Janusz Zaslavsky, which became the permanent seat and administrative centre of the vast Sanguszko estate.

As a natural consequence, Paweł Karol founded a temple for Nowy Zasław. As guardians, the magnate chose the Order of Missionaries, who accepted the foundation in 1747. After Sanguszko's death, Barbara of the Dunin family confirmed the foundation and undertook to continue financing the construction. The designer of the new church and monastery foundation was the Italian architect working at the Sanguszko court, Paolo Antonio Fontana (1696-1765).

Missionary Church - construction
. Work progressed very quickly and by the end of 1749, in less than three years, the church and monastery were already complete. By 1751, the entire church had been plastered and the furnishings inserted, which were also designed by Fontana. The main altar was made by the sculptor Jan Paszkowski, who was brought from Krzemieniec, while the side altars were supplied by the woodcarvers Wawrzyniec Sokołowski from Lviv and Grzegorz Zdanowski from Ostrog.

The completed and fully equipped temple was consecrated as St Joseph's Church in 1751. In 1755, a stone statue of Immaculata was placed in front of the façade by the sculptor Jan Pusz from Annopol.

Fontana designed the religious complex so that it faced the old chateau. In this way, he created a clear urban layout for Nový Zaslavl, combining a temple and residence, later enlarged by the new Sanguszko palace and garden layout.

Missionary Church - architecture
. The façade of the Missionary Church is particularly picturesque. The façade of the Church of the Missionaries of the Sanguszkos is of a pagoda shape, much wider than the outline of the body of the church, and additionally finished with square three-storey towers, connected with the church by galleries on the plan of an open ellipse.

The pilaster divisions and especially the second storey of the façade, with its slightly obtuse shape, lend fluidity to the whole establishment and enrich the decorative effect. The origins of this solution can be found in the architecture of Rome (the Church of Sant' Agnese in Agone in the Piazza Navona) and Turin (the work of Filippo Juvarra, including the Church of Sant'Umberto in the Venaria Reale).

Slightly earlier than the one in Zasław is the similarly composed façade of the Church of the Missionaries in Tykocin, founded by Grand Crown Hetman Jan Klemens Branicki.

Missionary Church - further fate
. The Sanguszkos took care of Zaslavl and St Joseph's Church until the Bolshevik Revolution (1917), when they were forced to leave their Volyn estate. The Soviet authorities closed the church in 1934 and used it as a military warehouse. The interior was ransacked and the furnishings destroyed.

The church returned to worship briefly during the Second World War. After the end of the war, it was again used as a warehouse and a truck access opening was pierced in the façade. From the 1970s onwards, the church premise stood abandoned, and makeshift repairs were carried out by local forces from 1988 onwards.

The church was returned to the Roman Catholic community in 1991. Since then, continuous repairs and restoration work has been carried out to restore the foundation to its original appearance.