Gengenbach Abbey was an Imperial Benedictine Abbey from the late Carolingian period to 1803. It was founded by Saint Pirmin (d. 735) sometime after his expulsion from Reichenau in 727 and settled by monks from Gorze Abbey. It enjoyed good relations with the Carolingian dynasty and soon became an Imperial abbey, with territorial independence. In 1007, however, Emperor Henry II presented it to his newly founded Prince-Bishopric of Bamberg.
Gengenbach was deeply embroiled in the Investiture Controversy and two of its abbots were driven out for supporting the Imperial rather than the Papal cause. Shortly after this, the abbey was involved by Abbot Theoger (1080–1139) of St. George's Abbey in the Black Forest and Bishop Otto of Bamberg in the Hirsauer Reform, during which the abbey church was demolished and rebuilt to the Hirsau model. Subsequently, it has been remodelled in the Gothic, Baroque and neo-Romanesque styles.
During the 13th and 14th centuries, the abbey was instrumental in developing the town of Gengenbach to economic maturity. The abbey avoided further monastic reforms, and although in danger of suppression during the Reformation, survived that too.
In 1575 and 1580, the abbey applied for membership of the Imperial College of Prelates but was refused, due to concern about its Imperial immediacy and Vogtei; membership was eventually approved in 1645 but this approval was not implemented until 1751. The abbey was mediatized in the wake of the German Mediatisation of 1803, and shortly afterwards its territories were absorbed into the state of Baden. However, the abbey was left to function under the last abbot until 1807 when the Grand Duke ordered it secularized.
References:The Chapel of St. Martin is the only completely preserved Romanesque building in Vyšehrad and one of the oldest in Prague. In was built around 1100 in the eastern part of the fortified outer ward. Between 1100 and 1300, the Rotrunda was surrounded by a cemetery. The building survived the Hussite Wars and was used as the municipal prison of the Town of the Vyšehrad Hill.
During the Thirty Years’ War, it was used as gunpowder storage, from 1700 to 1750, it was renovated and reconsecrated. In 1784, the chapel was closed passed to the military management which kept using it as a warehouseand a cannon-amunition manufacturing facility. In 1841, it was meant to be demolished to give way to the construction of a new road through Vyšehrad. Eventually, only the original western entrance was walled up and replaced with a new one in the sountren side. The dilapidating Rotunda subsequently served as a shelter for the poor.