The 14th-century Holy Trinity Chapel situated on the Castle Hill is one of the most important places in Lublin. The reason for this are the Rutheno-Byzantine paintings placed inside to decorate its interiors upon an order issued by King Władysław Jagiełło in the 1st half of the 15th century. The paintings depicting religious themes in the spirit of the Orthodox Church adorn the walls of the Roman Catholic church, which creates a unique symbol of the coexistence of Eastern- and Western-European cultures. Among the images of saints and Bible scenes, you can notice frescos depicting Władysław Jagiełło himself. These are the only images of the king created in his lifetime.
In 1899, the painter Józef Smoliński paid attention to fragments of polychrome visible under a layer of lime-based whitewash. He uncovered the scene on the staircase leading to the matroneum and made a copy and description of it, aptly linking the picture with the image of the founder of the paintings. The accidental discovery of Smoliński met with interest from the Academy of Learning in Krakow, as well as the Tsar's Archaeological Commission in St. Petersburg. In 1917, the first works on polychrome maintenance began. The events of World War II and the post-war decade significantly contributed to deterioration of the paintings. In 1976, the last, comprehensive stage of securing the chapel’s building technically and conservation of the polychrome begun. The original paintings were uncovered under many repaints, repairs and plaster patches. The long-standing maintenance was completed in 1997.
In 2015 the Chapel was honoured with the European Heritage Label.