Six kilometers into the reserve, the trail moves through wetlands that shelter two species you came to Patagonia hoping to see: the endangered huemul, for which this valley is one of Argentina's last strongholds, and the torrent duck, which nests here in stable, closely monitored numbers.

This isn't backdrop scenery; it's active conservation ground, and your guide will walk you through exactly what's being protected and why.

The trail opens onto Milodón Lagoon itself, a valley framed on every side by mountains and glaciers, with none of the trail traffic you'd find inside the National Park. Lunch is taken right at the water's edge before the return walk; six hours out and back, at a pace built for looking, not just covering ground.