More than 2,000 years after his death, Julius Caesar remains one of history’s most momentous figures. His military and political achievements transformed ancient Rome and left a legacy that still endures—from our idioms (“crossing the Rubicon”) to our calendar. The following are six of the most important legacies of the renowned Roman military commander and dictator.

1. Caesar expanded Roman rule in Europe.
After being appointed governor of Rome’s northern territory of Gaul in 58 B.C., Caesar vastly extended the boundaries of the Roman Republic across Europe, all the way to the shores of the Atlantic Ocean and English Channel. During the bloody eight-year Gallic Wars, his legions conquered local tribes in present-day France, Belgium and Switzerland.