Tradition relates that about the seventh century of the Christian era a nation of Indians, bearing the name of Caras, invaded the sea-board of central Ecuador. They were warlike, aggressive, conquerors by instinct, and their civilisation was superior to that of the barbarous tribes upon whom they descended. They came by way of the sea, most probably from the south, bringing a complicated religion to which they were fanatically devoted, and a military and tribal organisation which gave them an overwhelming advantage. In all probability the Caras were akin to those highly civilised nations who lived in the valleys of the northern Peruvian coast. Be this as it may, there is no doubt that the Caras were not long content with dominance along the coast, and succeeded in forcing their way up the slopes of the Cordillera through a zone uninhabitable on account of the perpetual rain, and only penetrable along defiles where the soaked clay of the steep mountainsides affords no footing and the tangle of vegetation leaves no path. At six thousand feet above sea-level the roads became better, the vegetation ceased to be tropical, and when they emerged through the passes to the comparatively level plains about Quito, some eight thousand feet above the sea, they found themselves in a country where the cereals and fruits of the temperate zone flourish and no forests interrupt communication. Two lines of great mountains stretched north and south and between them lay a plateau less than forty miles in width, and though much of it was bleak and arid, at least half lay below the elevation where the successful cultivation of the cereals and the potato becomes possible. At regular intervals transverse ranges of mountains, called "nudos," or knots, cut the plateau into separate divisions, each measurably protected from attack by its neighbours. Andean Ecuador has been aptly compared to a great ladder four hundred miles long, with the "nudos" forming its gigantic rungs. Beginning at the northern boundary of modern Ecuador, Quito lies in the second of the eight sub-plateaux, which is one of the largest and most fertile. Into it descended the Caras and began to conquer and absorb the aborigines. These inter-Andean valleys were inhabited by numerous tribes speaking distinct languages, who had developed considerable skill in agriculture. The compact and efficient military organisation of the Caras gave them a great advantage over more loosely organised peoples, but for three hundred years they were occupied in extending their power over the valley of Quito and thence over Latacunga and Ibarra, which adjoin it north and south.