The temple of Divus Hadrianus was an innovative structure which demonstrated a number of architectural features that emphasised Hadrian’s ruling ideology, as well as his fondness for Greek culture. First, the use of Greek Proconnesian white marble helped to emphasise its “simplicity,” but was also symbolic, taking the place of the marble from the caves of Luna, in central Italy, which had been used from the Augustan period onwards (Corradetti, “Architettura templare,” p. 48). The temple was also partially painted, for example, with the Corinthian capitals painted in gold. Yet, the overall impression from the outside was that of a simple, whitewashed structure. The temple was set inside a temenos (a sanctuary or holy precinct), much like various Greek-Hellenistic temples. Yet, in contrast with the Temple of Venus and Roma, the temple stood on a high podium and was entered through a flight of steps located at its front. However, the choice of the Corinthian order emphasized its similarity with other Roman temples. Another original feature was the use of polychromy, emphasised by use of the sober white Proconnesian marble set against the yellow columns of giallo antico marble, that were used to decorate the portico, and the red marble slabs of peperino, which decorated the inner space of the temple. The use of different marble slabs, creating a multi-coloured effect, is also present in another of Hadrian’s buildings on the Campus Martius, in the interior of the Pantheon, which seems to have acted as a partial model for the interior of the Hadrianeum; both spaces are topped by a barrel vault and decorated with coffers, or sunken panels. The only difference lies in the fact that while in the Temple of Hadrian the barrel vault covered a rectangular space, the barrel vault in the Pantheon covered the interior of the circular dome (Corradetti, “Architettura templare,” p. 49-50).

Although the choice of the Campus Martius might appear an odd location for a temple to a deified emperor, it fits with Hadrian’s “urbanistic interventions” in that part of the city; he had rebuilt the Pantheon, restored the Saepta and the Basilica of Neptune, and also the Baths of Agrippa (Parisi Presicce, “The enclosure of the Hadrianeum,” p. 78). It was a logical spot in an otherwise crowded city for his temple to be erected. The choice of the Campus Martius may also have related to a religious connection; according to various legends, Romulus, the first king of Rome, disappeared in an area called palus caprae, “the goat’s marshes” (Ovid, Fasti 2.491). This spot was later identified with an area located in the central part of the Campus Martius, between the Pantheon and the Piazza della Minerva. Thus, Hadrian, or possibly his successor Antoninus Pius, may have wished to erect the temple in a location where the ascent to the sky, or apotheosis, of Romulus took place (Plutarch, Life of Romulus I.28; Life of Numa 2; Ovid, Metamorphoses XIV.812-828). There was indeed precedent for the imperial ‘monumentalisation’ of the Campus Martius too; it had been the area chosen for the tombs of Sulla and Julius Caesar, and at its furthest limits, on the shores of the Tiber, was erected the Mausoleum of Augustus, the Ara Pacis and the Horologium (Coarelli, “Il Pantheon e il Tempio di Adriano,” p. 238-241).

According to Filippo Coarelli, the erection of the temple mirrored the difficulties faced by Hadrian’s successor, Antoninus Pius, in having his predecessor consecrated as divus (Coarelli, “Il Pantheon e il Tempio di Adriano,” p. 238-241). The Historia Augusta relates that Hadrian’s political choices had left him with little favour or support in the Senate, which only agreed to his divinisation at Antoninus Pius’s insistence (Hadrian, 27.1-2; Antoninus Pius 5.1). Although this has been used to explain the late completion of the temple, which was not finished until 145 CE, seven years after Hadrian’s death, the Hadrianeum may well have been conceived of well in advance; the Temple of Matidia, Hadrian’s mother-in-law, had been laid out also on the Campus Martius, in between two porticoed buildings that must be the Basilicas of Matidia and Marciana mentioned in the ‘Regionary Catalogues’ of the fourth century CE (Coarelli, Rome, p. 292; for the Regionary Catalogues, see Jordan, Topographie, p. 539-574). In this sense, the deification of Matidia was a prelude to that of Hadrian, with her temple and the two basilicas anticipating the addition of the Hadrianeum to the east (Coarelli, Rome, p. 292). The huge complex within which the temple was situated marked a return to the political use of the area that had last reached its height under Augustus; with Antoninus Pius determined to honour his adoptive father in monumental fashion, the construction of the Hadrianeum marked the beginning of the Antonine dynasty’s acquisition of space on the Campus Martius, which was used for the proclamation of ceremonies connected with the imperial cult and its associated honours. The “altars, porticoed plazas, honorary arches and illustrated columns [were] the constituent elements of an organic architectonic complex built in the tradition of the magnificent imperial forums” (Parisi Presicce, “The enclosure of the Hadrianeum,” p. 78).

Yet, the major characteristic of the whole structure was twenty-four rectangular marble slabs, decorated with reliefs, which depicted the personifications of the Roman provinces. Located probably on the attic within the surrounding portico of the temple, the depiction of the different personifications of the provinces served to emphasize the power of Rome, the diversity of the peoples conquered, and the extension of the Roman empire (Parisi Persicce, “Sottomissioni dei vinti,” p. 61).