Todos estos edificios se hacen de diverso modo que en Europa: Estudio arqueoastronómico de las iglesias jesuíticas de Chiquitos

The study of the spatial layout of Christian churches has been of great interest since late Antiquity and the beginning of the Early Middle Ages, and has received a new impetus in recent literature when it was recognized that the orientation of their main axes represents a key feature of their architecture. From the earliest Christian communities, the orientation of the church allowed the faithful to pray facing the east, towards the rising Sun. Several authors were careful to point this out in their writings; in particular, prior to the Council of Nicaea (325 AD), the Apostolic Constitutions indicated: “And let it be, first, the elongated building, with its head facing east”. We present a detailed analysis of the spatial orientation of the historic churches located in the Jesuit towns of Chiquitania (Bolivia). We have measured in situ the main characteristics of eight churches currently standing and the ruins of a ninth construction. In all cases, we carry out a thorough survey of the landscape surrounding each church, trying to find some common pattern, possibly astronomical, that explains its orientations. To our list we also add the orientation measures of a tenth church based on work with plans and satellite maps. We complement our data with a detailed cultural and historical study of the characteristics of missionary towns. Unlike the churches of the Guarani towns of the historic province of Paraquaria where the meridian orientations stand out, in the case of the Jesuit churches of Chiquitos, half of the measured constructions show orientations that fall within the solar range, with three churches oriented equinoctially with high precision. We analyze the reasons for these orientations and delve further on the possible relevance that lighting effects could have had for the architects of these churches, which represent true hidden cathedrals in the virgin tropical forest.

💡 Research Summary

The paper presents an archaeo‑astronomical investigation of the orientation of ten Jesuit churches in the Chiquitania region of eastern Bolivia. Eight standing churches, the ruins of a ninth (San Juan Bautista de Taperas), and a tenth (Santo Corazón de Jesús) derived from satellite imagery and digital terrain models were surveyed. Using GPS and a compass, the authors measured each church’s longitudinal axis and corrected horizon altitudes with SRTM‑based digital elevation data to obtain precise azimuths.

The results show a split pattern: five churches are oriented within the solar range (azimuths between roughly 70°–110° eastward and 250°–290° westward), while the other five align closely with the cardinal north‑south axis. Notably, three churches—San Francisco Javier, Concepción, and San José—are oriented almost exactly east (≈90°) or west (≈270°) with errors under 2°, corresponding to the equinoctial sunrise and sunset points. This suggests intentional alignment to allow direct sunlight to illuminate the altar on the equinoxes, a feature that would have created dramatic lighting effects during liturgical celebrations.

The authors discuss two astronomical interpretations. First, the axes may have been chosen to synchronize interior illumination with specific solar positions (equinoxes or solstices), thereby integrating natural light into the sacred space. Second, the churches are situated along a central avenue that passes through the town square and a Jesuit courtyard containing a sundial; the alignment of the church, avenue, and sundial implies a coordinated urban plan that linked civic, educational, and religious functions with solar timekeeping.

Cultural and historical context is examined in depth. The Jesuits arrived in the late 17th century, establishing reductions that combined European Baroque architecture with local building techniques (timber columns, thatched‑clay roofs). Town planning placed the church on one side of a large plaza, with the main avenue running from the Betania chapel through the square to the Jesuit college and the church. This differs from the Paraquaria missions, where the church axis coincides with the plaza’s north‑south orientation. The Chiquitania layout thus reflects a deliberate adaptation to the open horizon and the tropical environment.

Architecturally, the churches are modest in structural complexity—single‑nave basilicas with three naves, a low‑pitch roof, and large windows—but they exhibit Baroque decorative elements that emphasize light. The authors argue that this “theology of light” aligns with broader European Baroque trends, where illumination symbolized divine presence. By orienting some churches toward the equinox sunrise/sunset, the Jesuits could harness natural light to reinforce theological messages and to mark the passage of time for the indigenous community.

Statistical analysis confirms that about half the sample falls within the solar azimuth range, while the remainder adheres to traditional east‑west or north‑south orientations. This mixed pattern indicates an evolution from strict adherence to early Christian orientation norms toward a pragmatic, locally informed design strategy. The integration of the church axis with the town’s central avenue and sundial further underscores the Jesuits’ intent to embed astronomical knowledge into daily life and worship.

In conclusion, the study demonstrates that the Jesuit churches of Chiquitania were not arbitrarily oriented; rather, their alignments reflect a sophisticated blend of liturgical tradition, Baroque aesthetic, local environmental constraints, and intentional use of solar illumination. These findings contribute valuable data to the fields of archaeo‑astronomy, colonial Latin American architecture, and the study of cultural adaptation in missionary contexts, and they suggest that future research should explore the interplay of lighting, ritual practice, and urban planning in other Jesuit settlements across South America.