The ancient city of Nikomedia, approximately 100 km east of Istanbul, enjoyed a high level of fame for over 600 years, serving as the capital of Hellenistic Bithynia and the eastern capital of the Empire during the Tetrarchy. Until now, however, there has been little in the way of material culture to demonstrate Nikomedia's celebrated status in antiquity, primarily because the modern city of Izmit lies directly over most of ancient Nikomedia.

This situation changed after a crippling earthquake in 1999, which toppled buildings in the Çukurbağ district of the city centre and led to rescue excavations there in 2001, 2009 and 2016. What emerged was one of the most sensational discoveries of the last twenty-five years: the audience hall of Nikomedia's Tetrarchic palace which was decorated with colossal statues and marble reliefs with much of their original polychromy still intact. Preliminary reports appeared in 2006, 2018 and 2020, but Tuna Şare Ağtürk has now provided us with a detailed assessment of the reliefs and their overall significance within Tetrarchic Nikomedia.

An introduction to the city's history and the rescue excavations is followed by an overview of sculptural technique, style and the polychromy. Her discussion then turns to the reliefs themselves, all of which she organises into three main categories: the Tetrarchs in war and triumph, the eponymous heroes of Nikomedia, and games and festivals in Nikomedia tied to the imperial cult, after which she provides a catalogue of the sixty-six reliefs discovered in the complex.

Although the figural decoration of the complex is her focus, the author provides a synopsis of the reliefs’ architectural setting, which featured a monumental staircase leading to a rectangular hall surrounded by columnar aediculae of two stories. The floor featured an opus sectile pavement, and the acanthus leaves of the pilasters were gilded, as were parts of the colossal statues that occupied the niches.

Based on the architectural elements found around the reliefs, the author considers them to have formed a high frieze above the first-storey architrave, and suggests that some of them may also have adorned the podium of the first storey's aediculae. Many of the imperial reliefs are truly remarkable: Herakles crowning an equestrian Maximian; an emperor, either Diocletian or Maximian, receiving a garland from Victory; an emperor battling four barbarians while on a rearing horse with lionskin saddle; an adventus of Diocletian and Maximian, each of whom is crowned by a Victory. The two emperors embrace, as in the Venice and Vatican Tetrarchic groups, and the high-backed chairs on their purple carts are similar to the one used for the adventus on the Arch of Constantine frieze.

Probably belonging to the same scene is an enthroned Roma seated on three shields and holding a globe topped by Victory. She is flanked by a personification of the Roman people and a group of togate Romans that includes at least one child. There are also reliefs of Athena and (probably) Ares fighting barbarians who wear Phrygian caps, and another that the author plausibly interprets as a scene of forced migration of barbarians. Judging by hair and costumes, both eastern and western barbarians are represented, although Athena and Ares triumph over eastern barbarians exclusively.

Only two reliefs survive from the Eponymous Heroes of Nikomedia group. One depicts a youthful nude male with Poseidon, a reclining river god and an eagle, which Ş.A. interprets as a scene of Nikomedia's foundation by either Astakos or Nikomedes I. The second one, showing Medea slaying her children, may reference an etymological connection between ‘Medeia’ and ‘Nikomedeia’. Within the third group there are reliefs featuring boxers, athletes, charioteers, a mahout riding an elephant, prize tables with money bags and crowns, and two tragic actors standing with a prompter. One of the reliefs is inscribed with the names of [ΟΛΥΜ]ΠΙΑ, ΔΕΙΑ and ΚΑΠΕΤΟΛΙΑ, probably referring to three of Nikomedia's agonostic festivals that had a connection to the imperial cult.

Ş.A. dates the construction of this complex and its relief decoration to the period between 286 and 293 – in other words, after Maximian had been appointed co-emperor with Diocletian and before the formal inauguration of the Tetrarchy, since there is no obvious appearance by the Caesars. She regards the adventus as a timeless scene intended to highlight the partnership of Diocletian and Maximian, and the barbarians as indications of generalised conquest rather than actual campaigns. This may well be correct, but one could just as easily interpret the imperial iconography as the commemoration of a specific historical event, which would be the adventus of Diocletian and Maximian in Rome for the Vicennalia celebration in 303, at which time the victory over the Persian king Narses was celebrated. There is general scholarly agreement that both emperors were participants in the celebration, which would explain the iconographic specificity of the relief, while the inclusion of the seated Roma and the personification of the Roman people surely places the scene in Rome itself. The Phrygian-capped barbarians would then refer to the recently concluded Persian campaign, thereby complementing the earlier victories in the west. Lactantius (14.2) notes that a section of the imperial palace was set on fire in 303, and the imperial hall with reliefs celebrating Diocletian's Vicennalia could have formed part of the reconstruction. If that is the case, then the Caesars would probably have been represented there, but since only a fraction of the full relief cycle has been unearthed, we will need to wait for future excavation to clarify the full cast of characters and the timing of the events depicted.

This new complex and its painted decoration have transformed our understanding of Tetrarchic imagery in the eastern empire, and the author is to be congratulated for her lucid account of the discoveries and the carefully considered analysis of the issues they raise. We now look forward to Ş.A.'s second volume on the architectural elements of the aediculated façades and the colossal sculpture set within them.