The Great Saint Martin Church (Groß Sankt Martin) foundations (circa 960 AD) rest on remnants of a Roman chapel, built on what was then an island in the Rhine. The church was later transformed into a Benedictine monastery.
In 1150, a fire destroyed much of Cologne and it is supposed that the entire church was destroyed. The Archbishop of Cologne Philipp I. von Heinsberg sanctified the new building in 1172, and the first phase of construction, the tri-apsidal structure was built, with three round apses meeting in the shape of a cross. This is the only element of the church still present today. The eastern end of the nave was completed before a further fire in 1185, as well as aisles on the Southside. At the northern apse, two Benedictine chapels were later added, built over the ruins of the previous abbey buildings.
In the middle of the 13th century, new walls for the three apses were completed, with larger windows. These provided a sought-after lightness to the interior. The nave was also made five meters longer, and the atrium in the west was built.
After the completion of the church in the 13th century, few modifications to the form of the church were undertaken. Most significant during this period were the various renovations needed for the four surrounding towers.
Reforms under abbots Jakob von Wachendorp (1439–1454) and Adam Meyer (1454–1499) provided a stronger financial footing for the Benedictine abbey. From this the inner decoration of the church was embellished, including figures from the altar, installed in 1509, that are still present today.
In 1707, the decaying interior walls were repaired and refurbished. Heinrich Obladen, then the abbot of Great Saint Martin, also purchased a new, larger organ for the church. New adornments for the Church took on a Baroque style, including golden bands for the pillars, dome and walls.
The church was badly damaged in World War II; restoration work was completed in 1985.
References:The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.