Everything starts with a desire to cross the Pyrenees, but a crossing that returns to the aspirations of yesteryear, draw a feature between the north and the south of the chain. Why ? Perhaps to make the imaginary of childhood live in Gascon Earth, with the Pyrenees in focus The desire to insert it, to take the height to better see what's going on, on the Iberian slopes. Making this magic constantly renewed, years later, at the crossing of the border by a neck, a peak, a tunnel, born of the surprise of the landscapes encountered, radically different from the French side, sweet tumble to the arid Sierras, but oh how welcoming. It is during one of these vagabonds on the map that the author likes as long as the thread of its crossing appeared to him. A vertical blue line thicker than others, cutting the north massif to the south. Note 0 ° As part of the map, this straight line materializes the location of the Greenwich meridian, a reference meridian chosen conventionally as origin of the longitudes on the surface of the earth globe. The challenge is seductive, look for an unprecedented mountain itinerary, certainly with some unusual passages, flirting with an invisible reference? Stay closer to the meridian without following him at the centimeter, with as a line of conduct a just dosage between the landscape interest, will have the places of passage? Hautacam, Luz-Saint-Sauveur, Gavarnie, Breach of Roland, the villages of Sobrabe, the Sierras of Ríos Balces and Vero, the presence of two of the three national parks of the massif? and the adaptation of the route to the relief. After many field tracking, this route was born: 176.5 km for 10 400 m of elevation, presented in nine sections, Lourdes, Catholic, Alquazar, Muslim, Sierra de Guara (Aragón) , two cities rich in a tremendous heritage. Any hiker can consider scrolling step by step, selecting sections, in full, or adapting it to its aspirations.