The people who lived in Gallia Belgica were called the Belgae. They were a group of tribes within the bigger country called Gaul, which covered all of modern France. According to Julius Caesar, the Belgae were different from the other Gauls. He said that the border between Belgica and the main Celtic part of Gaul was the Marne and the Seine rivers and that the border with Germania was the Rhine river. It is no longer certain what language or languages were spoken in Gallia Belgica, but historians know there was an influence of both Celtic and Germanic languages.