Context: Inns are buildings where travellers can seek lodging and, usually, food and drink. They are typically located in the country or along a highway. In Europe, they possibly first sprang up when the Romans built a system of roads two millennia ago.[citation needed] Some inns in Europe are several centuries old. In addition to providing for the needs of travellers, inns traditionally acted as community gathering places.

Question: How many thousand years ago did the Romans build their road system?

Answer: two