Leaving the house of Carvallo, an engineer who channeled the water of the Caramella to Tortosa, we will climb to the head of the ravine and reach one of the emblematic mills of the territory, the Mola Castellona. Throughout this excursion you will often feel very close to the sky, enjoying an unbeatable perspective of the ravine and the Ebro valley. And it is when descending when you will feel the vertigo and the impossibility of descending where the path is seen, where a hidden step awaits us, in the Air Hole. The name does not deceive.