What does the author consider a great accomplishment of Rome?

The Appian Way was the first military highway, this was Rome's greatest accomplishments. Other accomplishments were arches, concrete, bridges, arched roofs, and aqueducts.

This depends on who you consider to be the author. If the author in your case would be a famous old historian, then they would probably marvel at the architectural accomplishments of ancient Rome and how they were able to create such magnificent structures in such a short amount of time.