While Roman pragmatism found uses for the magnificent monumental areas constructed by numerous emperors, there was also the use of space itself as a display of power, no more amply expressed than in the complex of the Horologium Augusti, or Augustan sundial erected in the area of the Campus Martius to the north of the city, and built in relation to the mausoleum of Augustus and his altar, the Ara Pacis Augustae inaugurated in 9 B.C. The marble panels on the exterior of the altar enclosure instructed the Roman citizens in the benefits of Augustan rule and the imperial destiny of his heirs, making claims to dynastic political supremacy as being divinely sanctioned through its reference to Aeneas. The altar stood at the edge of a marble pavement measuring 160 by 75 metres with bronze inlaid lines mapping the hours of the day and months of the year, times indicated by the shadow of a massive 30 metre high red granite obelisk transported here to symbolise Augustus’s conquest of Egypt. On his birthday, 23 September, the shadow of the sundial’s gnomon was cast across the entrance to the enclosure of the Ara Pacis, linking the space of the city with the life of the emperor in a dramatic display of apparently cosmic power. The personal mythology of Augustus as offspring of the sun god Apollo was thereby expressed in physical terms through urban monuments.
Text and illustration from Eamonn Canniffe’s forthcoming book The Politics of the Piazza: Meaning and History in the Italian Square to be published by Ashgate in late 2007.