St. Bassus's Church (Slovene: cerkev svetega Basa; Italian: chiesa di San Basso) is a church on Prešeren Square (Prešernov trg; Italian: piazza Prešeren) in Koper, a port town in southwestern Slovenia.
The building, which dates from the end of the 16th century, at first served as a hospital of St. Nazarius and was consecrated as a church by Koper Bishop Paolo Naldini in 1706.
It has a Baroque interior with a single nave and a flat ceiling.
The rich Baroque interior furnishings include the main altar with images of St. Nazarius and St. Bassus, a statue of St. Bassus in the vestry, and a Romanesque crucifix from about 1120, later Gothicised, that was believed to have miraculous powers (Italian: Crocifisso miracoloso).
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