They were declared a World Heritage Site on 17 December 1994, due to being the model for monasteries and evangelism on the American Continent. They represent the adoption of an architectural style by the first Franciscan, Dominican and Augustinian missionaries, which included the use of open outdoor space. This use of open space in the planning of churches and monasteries was adopted through most of Mexico and in some other parts of Latin America. There is disagreement as to whether the monasteries represent a complete imposition of European design or whether they adopted certain aspects of indigenous ceremonial spaces. However, the use of open chapels and “capillas posas” or atrium corner chapels, in large atriums were a way of accommodating the first indigenous converts, who were not used to entering large enclosed structures. The atrium became essential as the meeting point between the evangelists and the indigenous.