Augustus
Augustus' reign laid the foundations of a regime that lasted, in one form or another, for nearly fifteen hundred years through the ultimate decline of the Western Roman Empire and until the Fall of Constantinople in 1453. Both his adoptive surname, Caesar, and his title "Augustus" became the permanent titles of the rulers of the Roman Empire for fourteen centuries after his death, in use both at Old Rome and at New Rome. In many languages, "Caesar" became the word for "Emperor", as in the German "Kaiser" and in the Bulgarian and subsequently Russian "Tsar" (sometimes Csar or Czar). The cult of "Divus Augustus" continued until the state religion of the Empire was changed to Christianity in 391 by Theodosius I. Consequently, there are many excellent statues and busts of the first emperor. He had composed an account of his achievements, the "Res Gestae Divi Augusti", to be inscribed in bronze in front of his mausoleum. Copies of the text were inscribed throughout the Empire upon his death. The inscriptions in Latin featured translations in Greek beside it, and were inscribed on many public edifices, such as the temple in Ankara dubbed the "Monumentum Ancyranum", called the "queen of inscriptions" by historian Theodor Mommsen.
Cleopatra
Cleopatra decided in her last moments to send Caesarion away to Upper Egypt, perhaps with plans to flee to Kushite Nubia, Ethiopia, or India. Caesarion, now Ptolemy XV, would reign for a mere 18 days until executed on the orders of Octavian on 29 August 30 BC, after returning to Alexandria under the false pretense that Octavian would allow him to be king. Octavian was convinced by the advice of the philosopher Arius Didymus that there was room for only one Caesar in the world. With the fall of the Ptolemaic Kingdom, the Roman province of Egypt was established, marking the end of the Hellenistic period. In January 27 BC Octavian was renamed Augustus ("the revered") and amassed constitutional powers that established him as the first Roman emperor, inaugurating the Principate era of the Roman Empire.