The Dominican Order probably arrived in Lublin in 1230. They built a wooden oratory of the Holy Cross, which was later replaced with a brick Church of St. Slanislaus Bishop and Martyr. The great fire of Lublin in 1575 considerably damaged the church. After the reconstruction, the church had a new barrel vault and a façade in a Lublin Renaissance style designed by Rudolf Negroni. One of the most important events taking place at the church was the celebration of a thanksgiving mass attended by King Sigismund Augustus after the signing of the Union of Lublin in 1569. The temple enshrined a fragment of the True Cross, brought to Lublin by the Bishop of Kiev Andrzej in 1420, which supposedly had miraculous powers. Unfortunately, in 1991 the holy relics were stolen and have never been recovered. In 1967 Pope Paul VI granted the Dominican church the title of a minor basilica. The Dominican monastery neighbouring the church was constructed in stages until the 18th c. Legend has it that the act of the Union of Lublin was signed in the refectory of the monastery. Since the last renovation works completed in 2012, historic exhibits connected with the order have been displayed in the northern wing of the building. The most valuable objects can be seen in the treasury.