The Arrayanes is one of Patagonia's set-piece rivers — a short, brilliantly clear run inside Los Alerces National Park connecting Lago Verde to Lago Menéndez, flowing past the ancient arrayán forest that gives the river its name. The water is famously transparent, slow enough in places to sight-fish individual browns and rainbows holding over pale gravel, demanding softly presented CDC emergers, ants and beetles fished on fine tippet rather than anything thrown with confidence. National Park access and ecological rules are strictly enforced along this stretch, including gear checks to protect against didymo, so plan for that before arriving streamside. It's as much a scenic pilgrimage as a fishing trip, and deservedly popular — book a guide and expect to share the river with other anglers making the same trip for the same reasons.

• Volcanic glacial