Most of the monasteries have a large atrium in front of the church, an open chapel, four chapels in each corner of the atrium, and atrium cross, Stations of the cross on the atrium walls, a roofed church, and the cloister area for the monks. Unlike churches built before and in the centuries after, the atrium played a critical role in these monasteries, built initially for the purpose of evangelization. Each monastery had only a handful of monks but hundreds of indigenous converts to whom to say Mass. Part of the reason was to accommodate the large numbers but also because pre-Hispanic rites were performed outside. For evangelization, the atrium and its accompanying open chapel were built first. The atriums are surrounded by low walls, none over five meters high, to give a more intimate feel but keeping the area outside. The open chapels were almost always built on the side of the main church and facing the same direction, towards the atrium. Since most indigenous peoples could not read or write, the churches and open chapels were painted with Biblical scenes in order to evangelize through the images. The atrium walls often have markings for the Stations of the Cross and four chapels, one in each corner. These are called capillas posas. They were used during processions, especially during Corpus Christi, holding the Host. In the middle of the atrium, a large stone cross was placed. On the outside of these early churches, crosses almost always appear without the figure of Christ. The reason for this is that the friars did not want the natives to link the old practice of human sacrifice to the new religion and thus use it as justification for the continuation of the practice.