The Baroque and Neo-Classicism periods have left significant monuments in Latvia but the names of their creators are often unknown. This is especially important in the case of Latgale or the former Polish Livonia where architecture and artworks of high quality are often difficult to attribute. Before WW II Polish art historians were interested in the work of Italian-born painter Filippo Castaldi (1734-1814) in various regions of the country, including Latgale. But a more comprehensive insight into this master's work became possible only after the publication of Professor Andrzej Ryszkiewicz's article in 1965. It should be noted that Latvian art historians in the late 1980s could only benefit from this article. Restoration works at the Kraslava St. Louis Catholic Church have again drawn attention to this name in the context of 18th century Latvian art history. In 2003 when the high altarpiece was put to restoration, a niche with a well-preserved Castaldi mural was discovered. Information on the life of Filippo Castaldi (Gastoldi, Gustelding) remains to be fragmentary. The painter was born in 1734 in Arpino, in the Frosinone region of Italy, but nothing is known about his childhood and studies. About 1760 he arrived in Poland, perhaps invited by the Bishop Zaluski; he is known to have found an employer in Polish Livonia close to that time. This was the Kraslava landlord Konstanty Ludwik Plater who had started the ambitious construction of his main residence - the Kraslava town complex and palace ensemble. 19th century sources referring to archive documents attest that this master has painted a number of altarpieces in the Kraslava St. Louis Catholic Church. These were retable compositions painted on a wall that illusively depicted both plastic formations and figural compositions of altarpieces. Part of the attic of the high altar retable that was repainted later has survived. The composition 'St. Louis Departs for the Crusade' painted on the wall in the altar niche on view now is as it was since the restoration of around 1820.