At Oropesa he heard from the barber-surgeon of the mysterious Guadarrama mountains, and of the valley that lay undiscovered and unknown for thousands of years until a hunter found there a tribe of people speaking a language unknown to anyone else and ignorant of the rest of men. Rough wild ways intersect the book. Thunder storms overhang it. Immense caverns echo beneath it. The travellers left behind a mill which "stood at the bottom of a valley shaded by large trees, and its wheels were turning with a dismal and monotonous noise," and they emerged, by the light of "a corner of the moon," on to the wildest heath of the wildest province of Spain, ignorant of their way, making for a place which the guide believed not to exist. They passed a defile where the carrier had been attacked on his last journey by robbers, who burnt the coach by means of the letters in it, and butchered all except the carrier, who had formerly been the master of one of the gang: as they passed, the ground was still saturated with the blood of one of the murdered soldiers and a dog was gnawing a piece of his skull. Borrow was told of an old viper catcher caught by the robbers, who plundered and stripped him and then tied his hands behind him and thrust his head into his sack, "which contained several of these horrible reptiles alive," and so he ran mad through the villages until he fell dead. As a background, he had again and again a scene like that one, whose wild waters and mountains, and the "Convent of the Precipices" standing out against the summit, reminded him at once of Salvator Rosa and of Stolberg's lines to a mountain torrent: "The pine trees are shaken. . . ." Describing the cave at Gibraltar, he spoke of it as always having been "a den for foul night birds, reptiles, and beasts of prey," of precipice after precipice, abyss after abyss, in apparently endless succession, and of an explorer who perished there and lay "even now rotting in the bowels of the mountain, preyed upon by its blind and noisome worms."