Among the places thus garrisoned by the Aztecs was Quauhquechollan,[253] a city containing thirty thousand inhabitants, according to the historians, and lying to the southwest twelve leagues or more from the Spanish quarters. It stood at the extremity of a deep valley, resting against a bold range of hills, or rather mountains, and flanked by two rivers with exceedingly high and precipitous banks. The only avenue by which the town could be easily approached was protected by a stone wall more than twenty feet high and of great thickness.[254] Into this place, thus strongly defended by art as well as by nature, the Aztec emperor had thrown a garrison of several thousand warriors, while a much more formidable force occupied the heights commanding the city. The cacique of this strong post, impatient of the Mexican yoke, sent to Cortés, inviting him to march to his relief, and promising a co-operation of the citizens in an assault on the Aztec quarters. The general eagerly embraced the proposal, and detached Cristóval de Olid, with two hundred Spaniards and a strong body of Tlascalans, to support the friendly cacique.[255] On the way, Olid was joined by many volunteers from the Indian city and from the neighboring capital of Cholula, all equally pressing their services. The number and eagerness of these auxiliaries excited suspicions in the bosom of the cavalier. They were strengthened by the surmises of the soldiers of Narvaez, whose imaginations were still haunted, it seems, by the horrors of the _noche triste_, and who saw in the friendly alacrity of their new allies evidence of an insidious understanding with the Aztecs. Olid, catching this distrust, made a countermarch on Cholula, where he seized the suspected chiefs, who had been most forward in offering their services, and sent them under a strong guard to Cortés.