The prolonged migrations of the Nahuas towards the North had not spread civilization uniformly amongst all the tribes encountered on the route. Thus, down to the sixteenth century, there still existed in the heart of Mexico tribes very little removed from the savage state, such as the Otomis or "wanderers;" whereas, in other districts, the Nahuas had established themselves on a footing of acknowledged supremacy and developed a brilliant civilization. Thus they founded at the extreme north of the present Mexico the ancient city of Tulan or Tullan, the name of which passed into that of its inhabitants, the _Toltecs_, and this latter, in its turn, became the designation of everything graceful, elegant, artistically refined and beautiful. Ethnographically, it simply indicates the most brilliant foci of the civilization imported from Central America. In fact, there never was a Toltec empire at all, but simply a confederation of the three cities of Tullan, Colhuacan and Otompan, all of which may be regarded as Toltec in the social sense which I have just described. Many other small states existed outside this confederation. It was destroyed by the revolt or invasion of more northern tribes, hitherto held in vassalage and looked down upon as belonging to a lower level of culture and manners. These tribes received or assumed the name of _Chichimecs_ or "dogs," which may have been a term of contempt converted into a title of honour, like that of the _Gueux_ of the Low Countries. Thus arose a Chichimec confederation, of which Colhuacan (the name given for a time to Tezcuco), Azcapulzalco, the capital of the Tepanecs, and Tlacopan, were the principal cities. At Tezcuco the Toltec element was still powerful. Cholula, a sacred city, remained essentially Toltec, and in general the Chichimecs readily adopted the superior civilization of the Toltecs. This was so much the case that Tezcuco became the seat of an intellectual and artistic development, in virtue of which the Europeans called it the Athens of Mexico. It was from the eleventh to the fourteenth centuries, according to the historians, that what may be called the Chichimec era lasted.