Before the 10th century, there are no traces to date of occupation of the site on which the city is now built. The city was built on a site with very special qualities. The Gave de Pau, which descends from the Pyrenees, was a river which was fairly difficult to cross, and for a distance of approximately , only three fords existed: from Nay to the east, from Orthez to the west and that of Pau, strategically located between the two. The northern extremity of a plateau, formed to a point, overlooks this ford of almost . In summary, it is an ideal natural location to control the passage and the arrivals from the Pyrenees, and a small monitoring station was built around the year 1000, a fort surrounded by a simple palisade.