The Reverotte is the Dessoubre's principal tributary and, depending on who you talk to, either the best-kept secret of the Doubs or just a smaller Dessoubre. It's both, really. Short — under thirty kilometres — it runs through the same limestone plateau and feeds the same big grayling down in the Dessoubre's lower reaches. Walking up it feels like being let into a private beat: narrow in places, pocket water in others, the occasional deep glide where you can cover three fish with the same cast if you're clumsy. The trout are mostly small and the grayling are mostly not, which is a pleasant inversion of how these things usually go. It's the kind of river you show up on with a single fly box and no particular plan, and leave with an evening's worth of stories you'll tell badly at the bar.

• Limestone