The best mules employed in the Sierra are obtained from the province of Tucuman in Buenos Ayres. Formerly the arrieros used annually to bring droves of several thousand mules through Bolivia and the Peruvian Sierra, selling as many as they could on the way, and taking to Cerro de Pasco those that remained unsold. During the Spanish domination, the mule trade was in the hands of the Government, to whose agents it afforded ample opportunity for the exercise of injustice and extortion. It was one of the most oppressive of the _repartimientos_.[78] Every Indian was compelled to purchase a mule, and was not allowed even the privilege of choosing the animal. The mules were distributed by the authorities, and were tied to the doors of the houses for whose occupants they were destined. After the distribution of the mules, a collector went round to receive the payment. During the war in Buenos Ayres the traffic in mules suffered very considerably. For the space of twelve years not a mule had been brought from that part of South America to Peru, when in 1840 the Tucumanians revisited the Sierra with their droves of mules. They were joyfully welcomed by the Serranos, who gave good prices for the animals, and since then the traffic has begun to revive.
In tracing the characteristic features of the Sierra, I have as far as possible confined myself to generalities, and I will not now weary the reader by entering upon a minute description of particular towns and villages. All are built pretty nearly after one model. The large quadrangular Plaza is closed on three of its sides with buildings, among which there is always the Government house (_cabildo_), and the public jail; the fourth side is occupied by a church. From this Plaza run in straight lines eight streets, more or less broad, and these streets are crossed at right angles by others; all presenting the same uniformity as in Lima. The houses are roomy, surrounded by court-yards, and consist of a ground-floor and a story above, but very frequently of the ground-floor only. The walls are of brick, and the roofs are tiled. The churches are in very bad taste, with the exception of a few in the larger towns, which have a good appearance externally, and are richly decorated within. The smaller Indian villages are poor and dirty, and are built with little attention to regularity. But even in them the quadrangular Plaza is never wanting, and at least four straight streets issue from it.