The Gave de Pau commences in the high Pyrenees, in the wonderfully spectacular Cirque de Gavarnie, literally in a cascade falling nearly one thousand three hundred feet, perhaps the highest cascade known in the four quarters of the globe, or as the French say, "in the five parts of the world," which is more quaint if less literal. The Gave d'Oloron has its birth in the valley of the Aspe, and is a tributary of the Gave de Pau. It is what one might call pretty, but has little suggestion of the scenic splendour of the latter. The Bidassoa is one of the world's historic rivers. It forms the Atlantic frontier between France and Spain, and was the scene of Wellington's celebrated "Passage of the Bidassoa" in 1813, also of a still more famous historical event which took place centuries before on the Ile des Faisans. The Nivelle is a tiny stream which comes to light on Spanish soil, over the crest of the Pyrenees, and flows rapidly down to the sea at Saint-Jean-de-Luz, on the shores of the Gulf of Gascony. The Ministry for the Interior in France classes all these chief rivers as _flottable_ for certain classes of boats and barges through a portion of their length, and each of them as _navigable_ for a few leagues from the sea. Four great "Routes Nationales" cross the Basses-Pyrénées. They are the legitimate successors of the "Routes Royales" of monarchial days. The "Route Royale de Paris à Madrid, par Vittoria et Burgos," the very same over which Charles Quint travelled to Paris, via Amboise, as the guest of François Premier, passes via Bayonne and Saint-Jean-de-Luz. It is a veritable historic highway throughout every league of its length.