The main body of the St Mary's Church was built in the late 12th century and was probably rebuilt in the 1240s, including a tower, porches and north aisle, after being damaged by Llewelyn the Great in 1220. An upper level of clerestory windows was added during the 15th century. The tower originally had a timber spire clad in lead, though it was removed in 1802 after becoming dangerous.
The church's interior has a fine timber panelled ceiling with moulded beams, rafters and ribs, and carves bosses at the intersections. It dates to c. 1500.
The church organ dates from 1737, by Harris & Byfield, with two keyboards.
References:The church of the former Franciscan monastery was built probably between 1515 and 1520. It is located in the UNESCO World Heritage Site of Old Rauma. The church stands by the small stream of Raumanjoki (Rauma river).
The exact age of the Church of the Holy Cross is unknown, but it was built to serve as the monastery church of the Rauma Franciscan Friary. The monastery had been established in the early 15th century and a wooden church was built on this location around the year 1420.
The Church of the Holy Cross served the monastery until 1538, when it was abandoned for a hundred years as the Franciscan friary was disbanded in the Swedish Reformation. The church was re-established as a Lutheran church in 1640, when the nearby Church of the Holy Trinity was destroyed by fire.
The choir of the two-aisle grey granite church features medieval murals and frescoes. The white steeple of the church was built in 1816 and has served as a landmark for seafarers.