Œil de la Doue
A spring north of Martel issuing from a horizontal bedding plane at the foot of a 15 m cliff, reached by a 600 m footpath. In drought a 30 m lake leads to a sandy gallery and the first sump (195 m at -6.5 m in high water). Sump 2 is 354 m long (-16 m) and sump 3 runs 1,380 m with a low point at -52 m, followed by further sumps; the system is about 3 km long.
depth: 0–52 m