According to legend, the three-aisled basilica was founded by Rudolf II of Burgundy and Berta of Alamannia and dedicated to Saint Maurice before the Bernese Reformation in 1528. It is part of a group of churches that were probably built on Lake Thun before the year 1000, and whose architectural style shows Lombard influences. It was built in place of a previous building that was built around 700. It was built at a time when the western half of what is now Switzerland did not yet belong to the Holy Roman Empire. The border between Swabia, which belonged to the empire, and Upper Burgundy was defined by the Huttwil-Aarwangen-Basel line. It was not until 1033 that Upper Burgundy and thus also the western part of what is now Switzerland fell by inheritance to the Frankish Emperor Conrad II of the House of Salian.
This affiliation with Burgundy probably also explains the significant differences to church buildings in the area of the Holy Roman Empire at the same time. Unlike most churches in the empire, Amsoldingen lacks a transept and, to begin with, a tower in the form of a westwork.
Like the Spiez Castle Church, it is a pillar basilica without a transept, originally with three apses and a high choir. It was originally built without a tower. The current tower was only built later in place of the southern apse, which was demolished for this purpose. However, parts of the foundations of the former apse can still be seen today.
It was connected to a secular canons' foundation, which was devastated when the Zähringens conquered the Bernese Oberland in 1191 and was rebuilt around 1200. The church tower was built in Gothic style around 1400. The canons' foundation was abolished in 1484. Shortly before the introduction of the Reformation in 1528, Johannes Haller, a fellow campaigner of Huldrych Zwingli, worked as a pastor in Amsoldingen, but had to leave Amsoldingen in 1525 because of his marriage. His most famous successor was Samuel Lutz, who lived in Amsoldingen from 1726 to 1738 and made the place a center of Pietism.
In 1812, Johann Jakob Weber built the current organ. Roman spolia from Aventicum and Allmendingen are walled into the crypt, which dates from around 1200. The colored choir windows by Max Brunner (* 1910) symbolize God the Father, Son and Holy Spirit.
The church was extensively renovated from 1978 to 1980.
Source: Wikipedia