The exact date of the foundation of St. Catherine’s church in Karja is unknown, but it is believed that it was erected at the end of the 13th or the beginning of the 14th century. Probably from the very beginning it was intended not only as a place of religious worship, but also as a refuge in times of danger or war. This is evidenced by the rooms above the sacristy, that are not easily accessible, equipped with fireplaces, that could be designed to be able to house the congregation safely. In later times, churches like the one in Karja were probably used by pilgrims from Scandinavia traveling to Livonia. The fact that the church served as a stop for pilgrims, can also serve to explain how it obtained a rich, gothic decoration.
The church is a rather small building with a simple form. It has a single, non-tower nave with high vaults forming two spans, a simple chancel and a sacristy. What distinguishes the church is its rich interior decoration in the form of carved bosses of vaults, portals and capitals. The stone sculptures were probably made by successive generations of masters, probably craftsmen from Germany, Sweden and France in the style from romanesque to late gothic. Inside, there are also relatively well-preserved medieval wall paintings. Painted symbols probably have a pagan origin, among them are a triskelion, a pentagram, grotesque devils and other symbols of unclear significance. In addition, there are also more decorative paintings. The baptismal font from the 14th century and the crucifix from the 15th century deserve special attention from medieval equipment.