Of the legacies of the Roman Empire listed below, the most influential, effective, and lasting is:

The legacy of Roman law, justice, and the political system represents one of the most influential and enduring aspects of the Roman Empire. This legacy established foundational principles of governance and legal frameworks that have been integrated into many modern legal systems around the world. Concepts such as codified laws, the presumption of innocence, and the right to a fair trial can trace their origins back to Roman legal traditions.

Moreover, Roman political practices, including elements of republicanism and representations of citizenship, have profoundly influenced modern democracies. The Roman Republic's complex system of checks and balances, designed to prevent the concentration of power, has inspired countless political theorists and systems since.

While Latin as a language has certainly had a lasting impact on the Romance languages and modern scientific terminology, and Roman engineering is admired for its innovation and utility, the institutional aspects of law and governance form the backbone of civil society and order. The writings of poets and historians, while culturally significant, have less direct impact on the operational structures of societies. Thus, the legacy of Roman law and political systems stands out as both effective in its function and lasting in its influence on subsequent civilizations.