The site has been occupied since at least the Gallo-Roman era. However the first references to Pau as a settlement only occur in the first half of the 12th century. The town developed from the construction of its castle, likely from the 11th century by the Viscounts of Béarn, to protect the ford which was a strategic point providing access to the Bearn valleys and to Spain. The city takes its name from the stockade ("pau" in Béarnese) which surrounded the original castle.