The work presented in this paper is part of an international project about the Basilica of Nativity in Bethlehem, famous and ancient Church dating back to the late 6th century
and added in 2012 to the UNESCO world heritage list. Here we present a preliminary Computational Fluid Dynamics (CFD) study of indoor ow and temperature elds in
this still well-preserved building. In particular, the aim of the numerical simulation is to examine the impact of windows opening on indoor thermal equilibrium of the church,
characterized by a complex geometry. The computed air temperature in the steady-state regime and the time-history of air speed suggest that this simple but effective strategy
can improve both the thermal comfort during visiting hours and the conservation conditions for mosaics and mural paintings
