Between Sacred Tradition and Urban Form: An OpenStreetMap-Based Analysis of Church Orientation Patterns in Milan

Abstract. The orientation of Christian churches has long attracted attention in liturgical studies, architectural history, and archaeoastronomy. In the Catholic tradition, churches are often associated with an eastward-facing sanctuary and a westward-facing entrance, but in urban settings their realized orientation is also shaped by streets, neighbouring buildings, plot geometry, topography, and rebuilding campaigns. This paper investigates 114 church buildings in Milan using open geospatial data derived primarily from OpenStreetMap (OSM). A web-based analysis tool built with MapLibre GL JS and Turf.js was used to measure the azimuth from the building centroid to the selected entrance for each church. Entrance bearings were analysed with circular statistics and visualized with a rose diagram. The strongest concentration lies in the western and west-southwestern sectors. The mean direction is 245.4°, the mean resultant length is 0.283, and a Rayleigh test rejects circular uniformity (z = 9.101, p < 0.001). The result is stable for the 99 Catholic-tagged buildings, but an entrance-tag sensitivity analysis shows that the concentration is carried mainly by the 82 records explicitly tagged entrance=main. The findings reveal a statistically detectable but measurement-sensitive westward tendency, consistent with partial persistence of the traditional east–west liturgical axis alongside adaptation to urban form.