The Pantheon, roofed with the most spectacular dome of antiquity, is built in Rome by Hadrian

The emperor Hadrian, visiting Britain, orders the construction of a great wall from coast to coast to keep out the Caledonian tribes

Suetonius, librarian to Trajan and personal secretary to Hadrian, is well placed to research his racy Lives of the Caesars

The Sant'Angelo bridge in Rome, still standing today, is built for the emperor Hadrian by means of a coffer dam

The emperor Hadrian, with no children of his own, appoints a respected senator, Antoninus Pius, to succeed him

The emperor Antoninus Pius gives orders for the construction of a defensive earthwork, to the north of Hadrian's Wall

Marcus Aurelius, for long the designated heir, becomes emperor on the death of Antoninus Pius

The bronze equestrian statue of Marcus Aurelius, on the Capitol in Rome, begins a long European tradition of public sculpture

Marcus Aurelius is rare among emperors in writing twelve books of philosophical Meditations

On the order of Marcus Aurelius, Christians in Lyons are tortured to death - an instance of persecution unusual at this time

Plotinus, moving from Alexandria to Rome, teaches the influential philosophy later known as Neo-Platonism

The Christians of Rome use the catacombs as tomb chambers, and decorate the walls with murals on New Testament themes

The Picts win a dominant position among tribes in the northern regions of Britain, or Scotland

The emperor Aurelian, grateful for the apparent assistance of a Syrian sun god, establishes the cult of the Unconquered Sun - whose birthday is December 25

Diocletian, commanding an army near the Bosphorus in Thracia, is proclaimed emperor by his troops

Horses strong enough to carry men wearing armour are put to good use by northern barbarians, and by Romans in border regions such as Dacia

Diocletian resigns from his position as Augustus because of ill health, and retires to Dalmatia

Constantine's father, recently appoinnted Augustus in the west, dies at York and the young man is proclaimed Augustus in his place by the legions in Britain

Constantine, preparing for battle against a rival at the Milvian Bridge, orders his men to wear a Christian symbol, the Chi-Rho, on their shields

Constantine meets his co-emperor Licinius in Milan, and persuades him to follow a policy of encouraging the Christians

Warming to his new Christian role, Constantine summons more than 300 bishops to Arles to discuss the controversial issue of Donatus

Constantine founds several churches in Rome, among them the first St Peter's

Constantine's new churches in Rome introduce an important element in church architecture, the transept

Roman mosaic is at its most lavish in the floors of Piazza Armerina, in central Sicily

Constantine executes Licinius in Thessalonica on a charge of attempted rebellion, a year after defeating him in battle