The United States is often referred to as America or the U.S., likewise what we often refer to as Ancient Rome or the Roman Empire was actually known as Senatus Populusque Romanus or S.P.Q.R. This translates into "The Senate and the People of Rome." This moniker is somewhat misleading in that it implies two different sovereign entities, the senate and the People. But both were only sovereign at the leisure of Ceaser or the early Roman kings. It wasn't till much later that the modern conceptions of a Republic came to fruition in the 4th or 5th centuries. You can still see the initials S.P.Q.R. on the sewer grates throughout the city. Some of the more elaboratly decorated grates can be found in the streets surrounding the Vatican City.