The hardest part of this day is the distance, not the gradient. You climb steadily for hours on end, without it ever becoming truly steep. Even so, after a while you feel it in your legs.
The landscape grows rougher and emptier as you go. Around seven hours of walking calls for an unhurried pace and a few proper breaks, with your rucksack off. Give yourself that time.
At the end, Minas de Riotinto comes into view. You walk into a mining region where the earth is a rusty red. You won’t see that anywhere else on the route. You put down your rucksack, find a café terrace and look out over that strange, red landscape.