The Constantinian Basilica of the Lateran

Recent investigations at the Lateran by the present writers, with the indispensable collaboration of Professor Enrico Josi, and under the auspices of the Pontifical Institute of Christian Archaeology, have added considerably to our knowledge of the Constantinian basilica. The 4th-century foundation walls of this church are easily identifiable. They consist of massive baulks of concrete made principally with big fragments of grey-white marble which are obviously the product of the breaking-up of some quite important building, since pieces of architectural mouldings, capitals, ashlar, etc., frequently appear. During the past century (the first significant excavations date from 1851) such foundation walls have been exposed in many places, and an extensive system of vaults has been formed beneath the floor of the church as one investigation after another has added to our knowledge of the Constantinian building; to say nothing of the earlier structures on top of which the basilica was built, namely the Castra Nova Equitum Singularium of the early 3rd century, and certain rich private mansions which lie at a still lower level.