Helga Trefaldighet (Holy Trinity) Church was inaugurated in 1302. It replaced the previous church of local Ullerås parish. The church is made of grey stone and brick and it was originally a three-nave basilica. The western tower was added in the 15th century. The church was damaged badly by fire in 1702.
The interior is particularly notable. It is decorated with paintings by the famous medieval artist Albertus Pictor, which were created in the second half of the 15th century. Of particular interest is the depiction of The Visitation, regarded as one of the finest surviving medieval paintings in Sweden.
The Abbey of Saint-Etienne, also known as Abbaye aux Hommes ('Men"s Abbey'), is a former monastery dedicated to Saint Stephen (Saint Étienne). It is considered, along with the neighbouring Abbaye aux Dames ('Ladies" Abbey'), to be one of the most notable Romanesque buildings in Normandy. Like all the major abbeys in Normandy, it was Benedictine.
Lanfranc, before being an Archbishop of Canterbury, was abbot of Saint-Etienne. Built in Caen stone during the 11th century, the two semi-completed churches stood for many decades in competition. An important feature added to both churches in about 1120 was the ribbed vault, used for the first time in France. The two abbey churches are considered forerunners of the Gothic architecture. The original Romanesque apse was replaced in 1166 by an early Gothic chevet, complete with rosette windows and flying buttresses. Nine towers and spires were added in the 13th century. The interior vaulting shows a similar progression, beginning with early sexpartite vaulting (using circular ribs) in the nave and progressing to quadipartite vaults (using pointed ribs) in the sanctuary.
The two monasteries were finally donated by William the Conqueror and his wife, Matilda of Flanders, as penalty for their marriage against the Pope"s ruling. William was buried here; Matilda was buried in the Abbaye aux Dames. Unfortunately William"s original tombstone of black marble, the same kind as Matilda"s in the Abbaye aux Dames, was destroyed by the Calvinist iconoclasts in the 16th century and his bones scattered.
As a consequence of the Wars of Religion, the high lantern tower in the middle of the church collapsed and was never rebuilt. The Benedictine abbey was suppressed during the French Revolution and the abbey church became a parish church. From 1804 to 1961, the abbey buildings accommodated a prestigious high school, the Lycée Malherbe. During the Normandy Landings in 1944, inhabitants of Caen found refuge in the church; on the rooftop there was a red cross, made with blood on a sheet, to show that it was a hospital (to avoid bombings).