From Wikipedia

Roman Empire In The First Century

Years Of Trial

Augustus was succeeded by his stepson Tiberius, the son of his wife Livia from her first marriage. Augustus was a scion of the gens Julia (the Julian family), one of the most ancient patrician clans of Rome, while Tiberius was a scion of the gens Claudia, only slightly less ancient than the Julians. Their three immediate successors were all descended both from the gens Claudia, through Tiberius's brother Nero Claudius Drusus, and from gens Julia, either through Julia the Elder, Augustus's daughter from his first marriage (Caligula and Nero), or through Augustus's sister Octavia Minor (Claudius). Historians thus refer to their dynasty as "Julio-Claudian Dynasty".

Vespasian commissioned the Colosseum in Rome.

The early years of Tiberius's reign were peaceful and relatively benign. However, Tiberius's reign soon became characterised by paranoia and slander. He began a series of treason trials and executions, which continued until his death in 37. The logical successor to the hated Tiberius was his grandnephew, Gaius (better known as "Caligula" or "little boots"). Caligula started out well, but quickly became insane. In 41 Caligula was assassinated, and for two days following his assassination, the senate debated the merits of restoring the republic. Due to the demands of the army, however, Claudius was ultimately declared emperor. Claudius was neither paranoid like his uncle Tiberius, nor insane like his nephew Caligula, and was therefore able to administer the empire with reasonable ability. In his own family life he was less successful, as he married his niece, who may very well have poisoned him in 54. Nero, who succeeded Claudius, focused much of his attention on diplomacy, trade, and increasing the cultural capital of the empire. Nero, though, is remembered as a tyrant, and committed suicide in 68.

The forced suicide of Nero was followed by a brief period of civil war, known as the "Year of the Four Emperors". Augustus had established a standing army, where individual soldiers served under the same military governors over an extended period of time. The consequence was that the soldiers in the provinces developed a degree of loyalty to their commanders, which they did not have for the emperor. Thus the empire was, in a sense, a union of inchoate principalities, which could have disintegrated at any time. Between June 68 and December 69, Rome witnessed the successive rise and fall of Galba, Otho and Vitellius until the final accession of Vespasian, first ruler of the Flavian dynasty. These events showed that any successful general could legitimately claim a right to the throne.

Vespasian, though a successful emperor, continued the weakening of the Senate which had been going on since the reign of Tiberius. Through his sound fiscal policy, he was able to build up a surplus in the treasury, and began construction on the Colosseum. Titus, Vespasian's successor, quickly proved his merit, although his short reign was marked by disaster, including the eruption of Mount Vesuvius in Pompeii. He held the opening ceremonies in the still unfinished Colosseum, but died in 81. He was succeeded by his brother, Domitian, who had exceedingly poor relations with the senate. Domitian, ultimately, was a tyrant with the character which always makes tyranny repulsive, and this derived in part from the fact that he had no son, and thus was constantly in danger of being overthrown. In September of 96, he was murdered.