You leave Tarna behind just as the village is waking up. That early start is no luxury. You have a long day ahead of you, a good 9 hours of walking if you don’t stop too often to take in the view.
The route mostly goes downhill. That sounds friendly enough, but your knees will disagree. All that descending, well over 1200 metres, settles into your thighs. The climbing is manageable. It’s the distance and the descents that count, kilometre after kilometre. Take your time, plant your poles deliberately (if you have them) and eat something in good time. When the first houses of Rioseco appear, you walk the last few metres on autopilot. Rucksack off, shoes off, legs up.