The History of Rome (German: Römische Geschichte) by Theodor Mommsen is one of the most important works of nineteenth century classical scholarship. Mommsen moved beyond the criticism of literary sources pioneered by Niebuhr, rejecting much of the traditional narrative of Rome's foundation as mythical, and introducing other forms of evidence such as inscriptions painstakingly collected from around the former Roman world. Still occasionally cited today, Mommsen's history combines an extended narrative of Rome's internal and external political development from its earliest years to the reign of Augustus, with frequent digressions on the culture and society of the republic and its neighbours.
E.H. Carr conjectured that Mommsen's admiration for Caesar reflected his frustration with the failure of the revolution of 1848 in Germany. It may be that very sense of involvement that brings this work to life.
Free online texts
ClassicLiterature.co.uk: History of Rome. English text, HTML format.
Gutenberg: The History of Rome (Volumes 1-5). English text, Multiple formats.
Wikisource: The History of Rome (Mommsen). English text, HTML format. Currently first few chapters only.
Zeno.org: Römische Geschichte. German text, html format.
Librivox: Römische Geschichte. German language audiobook.
The Great Conversation: Further reading at Tom's Learning Notes
Polybius: The Histories.
Butler: Atlas of Ancient Geography.