The Minor Basilica of the Holy Trinity and the Sanctuary of the Relics of the Holy Cross is an important church located on Święty Krzyż (Holy Cross) in the Świętokrzyskie Mountains, within the Diocese of Sandomierz. It is the oldest Polish sanctuary, which gained particular significance from the 15th century. The temple has a rich history dating back to the 12th century, when Bolesław Wrymouth (Bolesław Krzywousty) founded the first Romanesque-style church. Over time, after the relics of the Holy Cross were donated by Władysław Łokietek, the church received a new dedication. In the 15th century, it was expanded with Gothic elements, and during the Jagiellonian period, it became a key place of worship, visited by many monarchs, including Władysław Jagiełło and Casimir Jagiellon (Kazimierz Jagiellończyk). In the 17th century, the church underwent a Baroque reconstruction, and after damage in the 17th century and a fire in 1777, a new church in the Baroque-Classicist style was built between 1781 and 1789. The interior of the church is characterized by classicism, with the main altar by Franciszek Smuglewicz and 18th-century choir stalls. The sculptures and polychromes in the sacristy are also unique. In addition to its religious function, the basilica plays an important role in the cultural heritage of the region, organizing indulgence festivals and pilgrimages. In 2013, it was granted the status of a minor basilica, and in 2014, its tower was rebuilt. Finally, it is worth noting that in the Oleśnicki Chapel, which is part of the complex, the relics of the Holy Cross are kept, attracting many faithful. The entire abbey complex is listed in the register of monuments, confirming its architectural and historical significance.