South of the Ebro the ground changes: this is the Sistema Ibérico, not the Pyrenees — a country of limestone and spring-fed ravines where the Piedra and the Mesa cut down toward the Jalón above Calatayud. The pick of the fly water is the Hoces del Río Mesa between Jaraba and Calmarza: a signed catch-and-release trout stretch of just under 2 km through red-rock gorge, from below the Jaraba bottling plant up to the road tunnel on the Z-453, with the road alongside the river for easy access. The Piedra is trout water too, but not where most visitors meet it — the kilometre through the Monasterio de Piedra park, from the Argadiles bridge to the Frailes bridge, is closed to fishing all year, and below La Tranquera the river turns to carp and barbel. Go with light tackle and fine tippets: this is small, clear, cold-water fishing, spring-fed but high enough (the gorge sits around 800 m) that snowmelt still shows in spring.

• Limestone