A most interesting description is given by Sahagun of one of the edifices erected by the Toltecs in Tula. If true, it clearly shows that in pre-Aztec times much more elaborately decorated buildings were erected than in the more recent period, for there are no accounts in the writings of the Spaniards of such lavishly ornamented buildings existing in the numerous cities conquered by them during the beginning of the sixteenth century. This is corroborated by the excavations now being conducted in the ruins of Teotihuacan, the greatest city known to us from Toltec times, where some marvelous structures have been unearthed.[54] The temple in question is said by Sahagun to have been built in honor of Quetzalcoatl, and included in its embellishment some of the most precious work of which they were capable. It had four halls. The eastern one (had the walls) covered with plates of gold, and it was called the golden hall or house. The western hall was called the hall of emeralds, or turquoises, because inside they had (the walls) covered with fine stonework, with all manner of stones, all placed and joined (together) as a coating or covering, like work of mosaic. The southern hall had the walls of divers marine shells, and in place of any other covering, they had silver, which was put together so nicely with the shells that the joints were not visible. The fourth hall, the northern one, had the walls made of colored jasper and shell, put on in a very ornamental manner.[55] The fame of this temple or palace seems to have been firmly established, as Sahagun recurs to it in another part of his history, but in less detail. Sahagun follows the fortunes of the culture hero while he was in the ascendency in Tula, and states that later, owing to circumstances which it is needless to relate in this place, Quetzalcoatl determining to abandon Tula, ordered the burning of “all the houses that he had made of silver and shell, and furthermore commanded that other precious things should be buried in the neighboring hills and ravines.”[56] This indicates that the mosaic-decorated building was laid in ruins, and part of the treasure, at least, was buried before the inhabitants left the region and commenced the migration southward. In presenting the tradition of this migration of Quetzalcoatl, Sahagun states that he (Quetzalcoatl) is reputed to have made and erected some houses underground which are called _Mientlancalco_. This of course refers to the famous ruins of Mitla, and seems to be an authentic tradition of the Nahuan origin of this important city of southern Mexico. It is doubly significant, when considered in connection with the description of the mosaic-decorated buildings in Tula, for, as is well known, the dominant architectural feature of the Mitla group of structures is the mosaic treatment of many of their outer and inner walls. [Illustration: PL. XI MASK OF WOOD (FRAGMENT) WITH MOSAIC DECORATION