Roman Emperors were rulers of the Roman Empire, wielding power over its citizens and military.
 The empire was developed as the Roman Republic invaded and occupied most of Europe and portions of northern Africa and western Asia.
 Under the republic, regions of the empire were ruled by provincial governors answerable to and authorised by the "Senate and People of Rome".
 Rome and its senate were ruled by a variety of magistrates – of whom the consuls were the most powerful.
 The republic ended, and the emperors were created, when these magistrates became legally and practically subservient to one citizen with power over all other magistrates.
 Augustus, the first emperor, was careful to maintain the facade of republican rule, taking no specific title for his position and calling the concentration of magisterial power "Princeps Senatus" (the first man of the senate).
 This style of government lasted for 300 years, and is thus called the "Principate" era.
 The modern word 'emperor' derives from the title "imperator", which was granted by an army to a successful general; during the initial phase of the empire, it still had to be earned by the 'Princeps'.
 The term emperor is a modern construction, used when describing rulers of the Roman Empire because it emphasises the strong links between the ruler and the army (on whose support the ruler's power depended), and does not discriminate between the personal styles of rule and titles in different phases of the Empire.
Marcus Licinius Crassus ( ; c. 115–53 BC) was a Roman general and politician who played a key role in the transformation of the Roman Republic into the Roman Empire.
 Amassing an enormous fortune during his life, Crassus is, excepting Augustus Caesar, considered the wealthiest man in Roman history.
Marcus Antonius (Latin: ; January 14, 83 BC – August 1, 30 BC), commonly known in English as Mark or Marc Antony, was a Roman politician and general who played a critical role in the transformation of the Roman Republic from an oligarchy into the autocratic Roman Empire.
The personal life of Marcus Tullius Cicero provided the underpinnings of one of the most significant politicians of the Roman Republic.
 Cicero, a Roman statesman, lawyer, political theorist, philosopher, and Roman constitutionalist, played a critical role in the transformation of the Roman Republic into the Roman Empire.
 A contemporary of Julius Caesar, Cicero is widely considered one of Rome's greatest orators and prose stylists.
The political career of Marcus Tullius Cicero began in 75 BC with his election to the office of quaestor, and ended in 43 BC, when he was assassinated upon the orders of Mark Antony.
 Cicero, a Roman statesman, lawyer, political theorist, philosopher, and Roman constitutionalist, reached the height of Roman power, the Consulship, and played a critical role in the transformation of the Roman Republic into the Roman Empire.
 A contemporary of Julius Caesar, Cicero is widely considered one of Rome's greatest orators and prose stylists.
The Senate of the Roman Empire was a political institution in the ancient Roman Empire.
 After the fall of the Roman Republic, the constitutional balance of power shifted from the "Roman Senate" to the "Roman Emperor."
 Beginning with the first emperor, Augustus, the Emperor and the Senate were technically two co-equal branches of government.
 In practice, however the actual authority of the imperial Senate was negligible, as the Emperor held the true power of the state.
 As such, membership in the Senate became sought after by individuals seeking prestige and social standing, rather than actual authority.
 During the reigns of the first Emperors, legislative, judicial, and electoral powers were all transferred from the "Roman assemblies" to the Senate.
 However, since the control that the Emperor held over the senate was absolute, the Senate acted as a vehicle through which the Emperor exercised his autocratic powers.
The Arch of Augustus (Italian: "Arco di Augusto" ) was the triumphal arch of Augustus, located in the Roman Forum.
 It spanned the road between the Temple of Castor and Pollux and the Temple of Caesar, near the Temple of Vesta.
 Built in 20 BC, it commemorated the return of the Parthian standards and replaced the earlier Arch of Octavian built on the same spot in 29 BC, to commemorate the Battle of Actium (31 BC) against Mark Antony and Cleopatra.
Gaius Julius Caesar (Latin: CAIVS IVLIVS CAESAR, ] , born: 13 July 100 BC – 15 March 44 BC), usually called Julius Caesar, was a Roman politician and general who played a critical role in the events that led to the demise of the Roman Republic and the rise of the Roman Empire.
 He is also known as a notable author of Latin prose.
The writings of Marcus Tullius Cicero constitute one of the most famous bodies of historical and philosophical work in all of classical antiquity.
 Cicero, a Roman statesman, lawyer, political theorist, philosopher, and Roman constitutionalist, lived from 106 to 43 BC.
 He was a Roman senator and consul (chief-magistrate) who played a critical role in the transformation of the Roman Republic into the Roman Empire.
 A contemporary of Julius Caesar, Cicero is widely considered one of Rome's greatest orators and prose stylists.
The history of the Constitution of the Roman Republic is a study of the ancient Roman Republic that traces the progression of Roman political development from the founding of the Roman Republic in 509 BC until the founding of the Roman Empire in 27 BC.
 The constitutional history of the Roman Republic can be divided into five phases.
 The first phase began with the revolution which overthrew the Roman Kingdom in 510 BC, and the final phase ended with the revolution which overthrew the Roman Republic, and thus created the Roman Empire, in 27 BC.
 Throughout the history of the republic, the constitutional evolution was driven by the struggle between the aristocracy and the ordinary citizens.

Question: What building was associated with a Roman politician and general who played a critical role in the transformation of the Roman Republic from an oligarchy into the autocratic Roman Empire?
Answer: Arch of Octavian