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.