In 1246, Counts Hartmann the Elder and Hartmann the Younger of Kyburg donated their lands, farms and forests in and around the village of Mülinen, as well as judicial rights over the village itself, to establish a Cistercian nunnery, which was placed under the authority of the abbot of Frienisberg in 1249 or 1250.
It was called in Latin Fons beatae Mariae, in German "Fraubrunnen", which replaced the existing village's original name of "Mülinen".
Over the following years it acquired further estates in a number of villages and vineyards on the shores of Lake Biel.
It owned houses in Bern, Burgdorf and Solothurn and received the Burgrecht in those cities.
[2] The vacated buildings became a castle and administrative center of the bailiwick of Fraubrunnen in the Zollikofen district.