Hadrian (76-138 A.D.) - Rome's maximum extent did not survive long after Trajan's death. Upon ascending the throne, Hadrian almost immediately gave Armenia and Mesopotamia back to the Parthians, and the Euphrates River became the empire's eastern border. Historians have speculated that Rome had reached its maximum manageable size, and in the years that followed, pressure from barbarian invaders would force it to start contracting. His reign lasted from 117 to 138. As emperor, Hadrian concentrated more on internal affairs. In fact, the construction of various defenses would indicate that he was more concerned about protecting Rome's borders, than expanding them. Hadrian's Wall is the most famous of these defenses; but he also built less permanent fortifications on mainland Europe, mostly along the Rhine and Danube Rivers. He traveled more than any emperor before him, visiting virtually every province in the empire. In 122, he even crossed the English Channel and went to Britannia. That was the year the wall which bears him name was begun and he oversaw the start of its construction. Shortly after that, he traveled to the eastern border and prevented a war with Parthia by negotiating directly with King Osroes I. Hadrian was also famous for his admiration of everything Greek. The Romans had long adopted Greek culture as their own, but Hadrian's love of Greece was greater than most. He traveled there more than to any other place and would frequently attend festivals, such as the Eleusinian Mysteries and Dionysia (the same Dionysia that was held in Athens during Classical Period). He also sent more money for building projects to Greece than any other province outside of Italy. Back in Rome, his biggest project was the rebuilding and upgrading of the Pantheon. And the most notorious uprising during his reign was the Bar Kokhba Revolt.