by Berthold IV, Duke of Zähringen. Its name is derived from German frei (free) and Burg (fort). Its most ancient part is conveniently located on a former peninsula of the river Sarine, protected on three sides by steep cliffs. The easily defended city helped the Dukes of Zähringen to strengthen and extend their power in the Swiss plateau in the area between the Aare and La Sarine.

Beginning at the time