Alt St. Maternus, Romanesque church in Rodenkirchen, Germany.

Alt St. Maternus is a Romanesque church in Rodenkirchen featuring thick stone walls and rounded arches that define its structural character. The building displays the robust construction methods typical of this architectural period, with columns and vaulting that support its interior space.

The oldest part, the nave with its semicircular apse, probably dates from the 10th century; a side aisle with Gothic windows was added in the 15th century and the massive west tower in the 17th century. Memorial stones found in the walls during restoration work by Heinrich Renard in 1925–29 point to an early Christian predecessor, since such stones were used only at churches with baptismal and burial rights. The church served as a parish church until the mid-19th century, when population growth, a catastrophic flood and a bequest of 15,000 Reichstaler from a local estate owner who died in 1857 led to the building of a new parish church.

The church is dedicated to Saint Maternus, an early bishop of Cologne whose veneration runs deep in this area. The name reflects the long religious history of this place and its importance to the local community.

The building is accessible by Cologne city train, particularly via lines 16 and 17, which offer direct connections to city centers and nearby areas. Visitors should know that the interior is generally accessible, though opening hours may vary depending on services or events.

On the outer choir wall facing the Rhine, a niche holds a figure of Saint Maternus at a boat's steering oar, wearing a mitre. Boatmen passing on the river once prayed to him for protection. Below it, a wave-ring frames Rodenkirchen's coat of arms with an anchor, Cologne's Saint Peter's key and the Berg lion.