What is the importance of Rome in the nonfiction book, The Early History of Rome: Books I-V?

Rome was founded by a leader named Romulus. He is the dominant of the two men who were viewed as or actually were the twins Remus & Romulus. The entire 'book of books' is based on the city and its history.

The city grows during the course of the book. However, the author lived when Rome was an expansive Empire. His writings about the ancient days of Rome's beginnings end long before the city has become an Empire but after it began to think of itself as an entire nation.