The true front door of the kingdom is formed by the passes at the other, the western, end of the Pyrenees. Here too we have three available routes, but they differ in character from the roads at the edge of the Mediterranean, in that they open up two completely separate lines of advance into Spain, and do not (like the Catalan defiles) all lead on to the same goal. All three start from Bayonne, the great southern fortress of Gascony. The first keeps for some time close to the seaside, and after crossing the Bidassoa, the boundary river of France and Spain, at Irun, leaves the fortress of San Sebastian a few miles to its right and then charges the main chain of the mountains. It emerges at Vittoria, the most northerly town of importance in the basin of the Ebro. A few miles further south it crosses that stream, and then makes for Burgos and Madrid, over two successive lines of Sierras. It opens up the heart of both Old and New Castile. The other two roads from Bayonne strike inland at once, and do not hug the Biscayan shore like the Irun-Vittoria route. They climb the Pyrenees, one by the pass of Maya, the other, twenty miles further east, by the more famous pass of Roncesvalles, where Charlemagne suffered disaster of old, and left the great paladin, Roland, dead behind him. The Maya and Roncesvalles roads join, after passing the mountains, at the great fortress of Pampeluna, the capital of Navarre. From thence several lines are available for the invader, the two chief of which are the roads into Old Castile by Logroño and into Aragon by Tudela. Pampeluna is quite as valuable as Vittoria as the base for an attack on Central Spain.