A capilla abierta or “open chapel” is considered to be one of the most distinct Mexican construction forms. Mostly built in the 16th century during the early colonial period, the construction was basically an apse or open presbytery containing an altar, which opened onto a large atrium or plaza. While some state that these were constructed by friars because the native peoples of that epoch were afraid to enter the dark confines of European-style churches, the more likely reasons for their construction were that they allowed the holding of Mass for enormous numbers of people and the arrangement held similarities to the teocallis or sacred precincts of pre-Hispanic temples. While open chapels can be found in other places in Spain and Peru, their systematic use in monasteries and other religious complexes, leading to a regularization of architectural elements, is only found in Mexico.
Structure
The capilla abierta was an open apse or presbytery of a reduced size, located on the ground floor or the first floor (which allowed for greater visibility) and opening onto a large atrium or plaza. The main idea is to allow the large number of people to congregate in front of a single altar. In Mexico, three types of open chapels came to be used: the "salon" or "mosque" type found in Cholula and Puebla, distinguished by its front arcade with Moorish arches; the "portico" type which was a porch area in front of the cloister; and the "balcony" type, located on the upper floor or roof. Portico style chapels can be seen in Tlalmanalco, Atlatlahucan and Cempoala, with the best known of the balcony type being found in Acolman, Mexico State.
Almost all open chapels were part of a larger structure, whether it was the main church or the cloister of the monastery. One significant exception is the chapel in Actopan, Hidalgo.
The most important feature of the open chapels was to allow the largest number of people possible to congregate in front of a single altar and have that altar visible to all. This is one reason why all capilla abiertas were built facing a large atrium or other open area. One of the most obvious features for visibility was to have the chapel located on an upper floor, such as the one located in Tlahueilpa. However, other architectural designs appear with this goal in mind. In San Juan Teposcolula, the buttresses holding up the roof were placed so that they did not block the view from any point in the atrium.
In some cases, the open chapel inspired designs for covered churches. The cathedral for Pátzcuaro was conceived of by Vasco de Quiroga as a center for the main altar with five naves surrounding it, so that anyone sitting anywhere in any nave could see the altar without problems. In reality, it would be five churches facing a single altar. However, only one nave was ever built. Another interesting church design with visibility in mind is the Royal Chapel of San Gabriel de Cholula. The chapel has a square floor plan with seven naves with seven sections each, separated by octagonal pillars. The inspiration for this design is the Islamic mosque. This design was also used at the Church of San Francisco de los Naturales in San Francisco de Mexico, which has since been destroyed. This same need may have also been the reason behind the later construction of single-nave churches with no side chapels later in the colonial period.
Purpose
The open chapel was predominantly used during the very early colonial period (16th century) in central Mexico, then called New Spain. Several examples appear in Cuzco, Peru, at the churches of Santo Domingo, La Merced and San Jeronimo, but their systematic appearance and regularization of appearance appears only in Mexico.
Some sources state that the capilla abiertas were constructed because the native populations in the 16th century were too afraid to enter the dark confines of European style churches. However, a number of these chapels predate their traditional church counterparts, sometimes by decades or more. The most likely reason for their construction was the fact that in the early colonial period, there was an enormous number of indigenous people and few friars and priests to evangelize and say Mass. The need for these chapels is mentioned by Toribio de Benavente who writes that they are needed along with large atriums to hold numbers of people who could not fit inside the church on Sundays and during festivals. During the slow times, such as mid-week, the main church was used. Another advantage the open chapel/atrium arrangement afforded was that it had similarities to the old teocallis, or sacred precincts of pre-Hispanic temples.