Adriano, famous for the renowned wall, was above all a great traveler. It is not clear whether he was designated to reign by Emperor Trajan, or, as seems more likely, he was adopted on Trajan's deathbed by his widow, Plotina, who concealed her husband's death for several days. He reigned from 117 to 138 AD and spent most of his reign traveling throughout the Empire. Devoted to the army to the extent that he slept and ate among the soldiers, always depicted in military attire, he benefited from a period of stability and increasing prosperity of the Empire, which allowed him to undertake long journeys and get to know closely the various realities of the imperial territory. He went to Gaul, Germany, Britain where he began the construction of the famous wall. He then traveled to Spain and the East, pausing in Athens, a city he particularly loved. In Greece, he undertook an intense program of building. Upon returning to Italy, he carried out major restorations and constructions, including the Pantheon of Agrippa, a circular mausoleum, the current Castel Sant'Angelo, and Hadrian's Villa in Tivoli, which covered about two hundred hectares.

He then went to Africa where he began fortifying the border with the desert, called the African trench. He then returned to the East and Greece once again.

During his stay in Egypt, Hadrian witnessed the death of his young lover Antinous, who was deified and a city named Antinopolis was built in his honor at the place where he died. He visited Judea, where he decided to found a colony in Jerusalem following the model of all Roman cities with plans to build a structure dedicated to Jupiter Optimus Maximus in place of the destroyed Jewish temple. This project led to a strong rebellion, which had already occurred under Trajan, resulting in a harsh repression. Over half a million people died, the political authorities of Judea were annihilated, and Jews were barred from entering Jerusalem for a long time.