The Prepirineo, or pre-Pyrenees, are the ‘foothills’ of the Pyrenees on the
southern side of the Spanish border with France. Although little appreciated outside Spain they are a walker's paradise. They combine great scenery, wildlife, historical interest, good local food, a huge choice of accommodation, good weather and a comparatively long walking season. With the help of my Spanish friend Juan Holgado, the expert on Spanish walking, I'm researching the area (an excuse for a series of Spanish holidays) and if it's as good as I think it is I will write a guide.
Defining where foothills start and finish is always a challenge and that's as true of the Pyrennees as it is of the Alps. The Prepirineo to an extent are defined by geology. The Pyrennees correspond to an exposed line of particularly old rock (known as the 'axial line' or 'primary axial line') with the Prepirineo formed by younger rock sitting either side of the ancient core. Geologically the Prepirineo are uplifted remnants of rocks that would originally have covered the older rocks in the middle, but being younger and softer they didn't last as long. Of course, with great slabs of rock folding and faulting over each other it's actually more complicated. In particular, it's not symmetrical and there are lots more of the younger, softer rocks on the southern
Spanish side of the core than on the northern side.