One of these roads passed over the grand plateau, and the other along the lowlands on the borders of the ocean. The former was much the more difficult achievement, from the character of the country. It was conducted over pathless sierras buried in snow; galleries were cut for leagues through the living rock; rivers were crossed by means of bridges that swung suspended in the air; precipices were scaled by stairways hewn out of the native bed; ravines of hideous depth were filled up with solid masonry; in short, all the difficulties that beset a wild and mountainous region, and which might appall the most courageous engineer of modern times, were encountered and successfully overcome. The length of the road, of which scattered fragments only remain, is variously estimated, from fifteen hundred to two thousand miles; and stone pillars, in the manner of European milestones, were erected at stated intervals of somewhat more than a league, all along the route. Its breadth scarcely exceeded twenty feet. *41 It was built of heavy flags of freestone, and in some parts, at least, covered with a bituminous cement, which time has made harder than the stone itself. In some places, where the ravines had been filled up with masonry, the mountain torrents, wearing on it for ages, have gradually eaten a way through the base, and left the superincumbent mass - such is the cohesion of the materials - still spanning the valley like an arch! *42 [Footnote 41: Dec. de la Aud. Real., Ms. "Este camino hecho por valles ondos y por sierras altas, por montes de nieve, por tremedales de agua y por pena viva y junto a rios furiosos por estas partes y ballano y empedrado por las laderas, bien sacado por las sierras, deshechado, por las penas socavado, por junto a los Rios sus paredes, entre nieves con escalones y descanso, por todas partes limpio barrido descombrado, lleno de aposentos, de depositos de tesoros, de Templos del Sol, de Postas que havia en este camino." Sarmiento, Relacion, Ms., cap. 60.] [Footnote 42: "On avait comble les vides et les ravins par de grandes masses de maconnerie. Les torrents qui descendent des hauteurs apres des pluies abondantes, avaient creuse les endroits les moins solides, et s'etaient fraye une voie sous le chemin, le laissant ainsi suspendu en l'air comme un pont fait d'une seule piece." (Velasco, Hist. de Quito, tom. l. p. 206.) This writer speaks from personal observation, having examined and measured different parts of the road, in the latter part of the road, in the latter part of the last century. The Spanish scholar will find in Appendix, No. 2., an animated description of this magnificent work, and of the obstacles encountered in the execution of it, in a passage borrowed from Sarmiento, who saw it in the days of the Incas.]