The Christianization of the Roman Empire corresponds to a unique phase in the history of Europe. This paper will thus focus on the role of material, visual, and ritual cultures in this process. I wish to demonstrate that adult initiation – including pre- and post-baptismal preaching, baptism, and the associated spaces – was the key-moment in the life-changing process of conversion. Indeed, the dramatic staging and setting within initiatory rituals enacted the real moment of inclusion into the Christian community. Luxurious buildings, lighting and images, were constitutive for these experiences. As can be perceived from ancient texts and monuments, it was in this multisensory environment that individual and collective Christianization was achieved. Such rituals also had an external impact: movements, architectures, sounds, smells, glittering images were projected on the cityscape. The public and communitarian dimension of the rituals had remarkable proselyte potential on the rest of society.