• Based on the basilica of the Theater in Messene the architectural planning and building practices in provincial monuments of the sixth century is examined. In the basilica’s impost capitals, the use of position- ing marks for the correct setting of the colonnades is observed and on the paved floor of the sanctuary auxiliary etchings are visible for the proper setting of the liturgical furnishing. This evidence offers insight into the process of building monuments like the Messenian basilica.