In this case, the text says that the duel would happen, not on the bank of the Gave the side of the Soule, but the shore-side of Navarrenx (Belluno Fiet Quod non in ripa Soulensi, sed in Sponda Navarrensis).

Indeed, the village is an important step on the road to Puy crossroads leading to the Somport pass to the east and to the west of Roncesvalles.

[4] The Viscount of Béarn built a magnificent castle Casterasse ("fortress") on the hill to the west, at the confluence of the rivers Gave d'Oloron and Arroder.

Henry II of Albret, the king of Navarre, decided to reinforce defences on the right bank of the mountain stream of Oloron.

From 1538 to 1546, fortification works were carried out under the direction of Béarn master builders François Girard and Arnaud de Mirassor, as per the design of Italian architectural engineer Fabricio Siciliano.

Later, a powder magazine would be built that would store up to 25,000 lb (11,000 kg) of gunpowder: a square-shaped construction little more than 9 m (30 ft) long, it was originally surrounded by a wall, part of which was visible aboveground.

The fortifications were tried and tested during religious wars under the reign of Jeanne of Albret, when the garrison under the command of the Baron of Arros successfully resisted a three-month siege in 1568.

From the top of the ramparts (for example, from the crenellation platform overhanging the Saint-Antoine gate), there is a pleasant view of the Pyrenees and, below, the arches of the bridge of Navarrenx (13th century).