The church of St. Mary Magdalene in Koeru is one of the oldest in the province of Järvamaa, because its origins date back to the middle or third quarter of the 13th century. It was mentioned for the first time in written sources in 1287. It was severely damaged during the Livonian War in the 16th century and during the Northern War in the early 18th century. During the reconstruction, it received a new top of the tower, roofs and sacristy, and in the 19th century a gallery was added to the interior.
The church has the form of a spacious hall, three-aisle and three-bay building, 35 meters long and 15 meters wide, consisting of a rectangular nave, quadrilateral chancel on the eastern side, wider than the central nave, and a quadrilateral, slender tower on the west side. On the northern side of the chancel, there was a narrow sacristy, while in the 14th century, a four-sided porch was erected in front of the northern entrance to the nave.
The church, despite the vaults in it, had no buttresses, probably due to the massive perimeter walls that fully took their weight. The raw façades of the church were pierced with tall but narrow pointed-arched windows. The window in the eastern wall, illuminating the altar, originally filled with a two-light tracery, received a more impressive form. Above it, there was also a simple opening that illuminated the attic above the vaults
Inside, the chancel was opened to the the central nave with an ogival arcade, a similar arcade was also placed in the western part of the church between the tower and the nave, which provided lighting for the central nave through a round oculus pierced above the entrance portal. The eastern arcade was originally separated by a rood screen, with the first floor accessible from the chancel through a passage in the thickness of the northern wall. This passage also provided access to the attic above the vaults.
A characteristic feature of the church was the large difference in the width of the central nave compared to very narrow aisles. They were separated by four slender cylindrical pillars supporting groin vaults and wide arch bands with a rectangular moulding, which were supported on the walls on the geometric corbels (one of them was decorated with a low-relief oak branch). The pillar capitals received a decorative form, with single, early Gothic motifs of leafs added to late Romanesque flagellar designs. The head of the north-west pillar was treated differently, with half of the figure of a hooded man pointing at his head. It probably depicted a Cistercian monk, because Koeru was located in the lands of the Falkenau (Kärkna) Cistercian monastery. The vaults and arches were decorated with architectural paintings, the area around the windows and the chancel arch were also painted.
The majority of the church has been preserved in its medieval form. Only the roofs and the top of the tower were replaced, burnt during the 18th-century warfare, the sacristy on the northern side of the presbytery is also a modern annex, although it was built on the site of the medieval one. The interior is mostly from the post-Reformation period, including the 19th-century gallery, but many original architectural details and fragments of old polychromes have survived.
Alttoa K., Bergholde-Wolf A., Dirveiks I., Grosmane E., Herrmann C., Kadakas V., Ose J., Randla A., Mittelalterlichen Baukunst in Livland (Estland und Lettland). Die Architektur einer historischen Grenzregion im Nordosten Europas, Berlin 2017.