St. Nicholas Cathedral in Białystok, built between 1843 and 1846, serves as the Orthodox cathedral of the Białystok-Gdańsk Diocese of the Polish Autocephalous Orthodox Church and is the seat of the St. Nicholas Parish. The structure, erected in the classicist style on a Greek cross plan, combines elements of Byzantine and ancient architecture. The interior of the church is adorned with an iconostasis from 1846, featuring works of the Vilnius school, and frescoes painted by Józef Łotowski between 1975 and 1976, depicting scenes from Christian life. The cathedral has been one of the key religious sites in Białystok, serving as a symbol of Polish and Orthodox traditions. The history of the exchange and desecration of sacred objects during the partitions and after World War II (e.g., the loss of the Icon of the Mother of God) influenced the development of local identity. An interesting aspect was the growth of the veneration of St. Gabriel of Zabłudów, whose relics are kept in the cathedral. Architecturally, the cathedral gains recognition through comparisons with other existing Orthodox structures in Poland and Russia, and its dynamic form, with its characteristic dome and bell tower, makes it an important landmark in Białystok's architecture. In 1992, a special ceremony took place for the translation of the relics of St. Gabriel, attracting a vast number of the faithful, further testifying to the importance of this temple in the religious life of the region. St. Nicholas Cathedral, as a listed heritage monument, is not only a significant religious building but also a place with a rich cultural history that blends Orthodox and local traditions with spiritual fervor.