Nate Andrade had a nice article in the most recent volume of the Journal of Early Christian Studies, titled, "The Processions of John Chrysostom and the Contested Spaces of Constantinople". In it, Andrade considers the role of processions, particularly those led by the controversial Patriarch John Chrysostom, in transforming urban spaces inscribed with "secular" or even pagan significance into spaces of Christian ritual. He set Chrysostom's actions against the dual backdrops of his longstanding criticism of secular institutions ranging from the baths to the theater and games (many of which date to his days in Antioch) and Chrysostom's battles with members of the Theodosian court in Constantinople. The use of processions, highlighted by singing psalms, obvious displays of Christian regalia, and perhaps even the Christian scents of incense, combated the secular or even demonic associations that Chrysostom saw in the chaotic, temptation filled, world of the Late Antique city.
Andrade's subtle article relies on the unprecedented textual sources for the city of Constantinople in the 5th century and the relatively substantial accounts of Chrysostom's controversial term as bishop of the city. (A similarly, if now somewhat dated account of the relationship between the city and church appears in Tim Gregory's Vox Populi). It's tempting to imagine how Chrysostom's use of processions in Constantinople would translate to cities where our textual evidence is more limited. For example, do the acclamations inscribed in public spaces in Aphrodisias (and so carefully analyzed by C. Roueché) commemorate a kind of processional practice similar to those employed by Chrysostom?
It is particularly valuable to consider how public processions expanded the range of liturgical practice from the space of the church building to the urban space and the community. As early as the early 4th-century, Licinius considered it a useful strategy of expel Christians from their churches and force them to hold their services outdoors or outside the walls of the city (Eusebius, VC, 1.53). This suggests that Chrysostom was not the first to challenge the secular or pagan nature of the city through Christian assemblies held outside the space of the church. J. Baldovin argues for a kind processional warfare between various groups of Christians in the city of Constantinople during the 5th century (Baldovin, The Urban Character of Christian Worship, 183-184). Andrade's article as well as earlier and later evidence suggests that urban space could well accommodate Christian liturgical practices which the clergy viewed as tool to sanctify secular or pagan places. This turns on its head the idea that Christian sacred space, namely church buildings, represented sacred spaces that were a kind of pre-condition for liturgical practices. While the presence of relics, iconography, and both functional and mnemonic architecture surely reinforced the suitability of the church for liturgical activities, the Christianized space did not require these features. In other words, Christian activities made places sacred in Late Antiquity.
The mobility and transferability of the Christian sacred within Late Antique society makes using archaeology to reconstruct Christian landscapes particularly challenging. With the exception of the kind of inscribed acclamations mentioned earlier, processional liturgies would leave very little physical evidence.