The megalithic monuments of Arles–Fontvieille appear to have been deliberately constructed such that a ray of the setting sun on and around the equinox penetrates the subterranean chamber producing a spectacular light-and-shadow hierophany. Moreover, at one of the sites there is evidence in the form of rock art that observations were also being made of heliacal rising and settings, possibly of both the Pleiades and Orion. The equinox hierophany has been documented at three of the four intact monuments of the group. This phenomenon was probably exploited for sacred ritualistic purposes related to seasonal change and timekeeping by the agricultural people who built the monuments. This evidence has significant importance for understanding these monuments in the context of European megalithism and the wider European Neolithic as well as for understanding their cosmological role within the society that built them.
