What is immediately striking in the representation of the male players is that they are so often depicted in some form of military dress.

This introduces one of the central paradoxes of this notional age of peace and harmony. For while the Emperor Augustus, a victorious general and founder of the imperial system, was seldom represented as a warrior, the emperors of the second century relentlessly emphasized this role.

The empire reached its greatest extent — an area of 3.5 million square kilometers, or 1.35 million square miles, with an estimated population of 55 million — during the reign of Trajan. Much of what he did to transform Rome is still visible from the Capitoline Museums or within a few minutes’ walk. The Trajan Forum was the largest and grandest of all the forums and the so-called Trajan Markets on the hillside above are well preserved. Nearby are the remains of the huge Trajan Baths on the Oppian Hill — the first to include a library, park and cultural complex — which was to serve as the model for all subsequent monumental baths. Vast infrastructure projects included a new port at Ostia, canals, quays, aqueducts and sewers.

But these improvements were mainly financed by war booty, especially what was gained from 101 to 106 during the conquest of Dacia — a kingdom centered on present-day Romania and Moldova.

These wars were celebrated in the spiraling friezes of Trajan’s Column on the edge of the Trajan Forum, the first column of its kind and the first depictions of an emperor on campaign. The Trajan Forum itself was adorned with multiple images of the Dacian Wars in the form of statues, reliefs and decorative elements of the victorious emperor and of defeated Dacians.

Hadrian, who had fought in the Dacian Wars, abandoned his predecessor’s policy of expansion and concentrated on consolidating the empire’s existing borders. But despite his image as a peacemaker, he put down the Jewish revolt led by the self-declared messiah Bar Kokhba (132-135) with resolute savagery, refounding Jerusalem as a pagan military colony. Hadrian, too, left his monumental mark on Rome, most prominently in the Pantheon and his mausoleum, now Castel Sant’Angelo.