Rome Metro C Line is the longest urban underground railway line in Italy and it is the first metro line in Rome to stretch beyond the Great Ring Road, thus bridging the gap between the farthest suburbs and the Historical Centre. It is an original project, carried out mostly underground at a depth of 25/30 metres. The main track put out to tender envisaged realization of a 25,6 km long line with 30 stations (10 of which resulting from the restyling of existing stations and 20 new underground stations).

Consolidation and impermeabilization of both excavated tunnels was achieved via the Artificial Ground Freezing Process, in order to ensure the greatest possible safety degree as far as both workers and existing surface structures were concerned.