In Roman times, Switzerland was not a single political unit. Its territory was divided between five different Roman provinces.

Once a new province had been pacified, Roman rule was not oppressive. The local elites kept their rank and prestige and gradually the entire population was Romanised. If the official language was Latin, the normal spoken language was a Celtic dialect.

The Romans built towns as administrative centres, where they also set up schools in which Latin was the language of instruction. It was only as the impact of this education spread into the countryside that Latin gradually replaced Celtic.

The area that is now Switzerland was an important transit route under the Romans, who improved and maintained the roads over several of the passes.

Towns were built or enlarged on the main routes. The three most important towns were Aventicum (Avenches) at a crossroads, Augusta Raurica (Augst, near Basel) on the Rhine, and Colonia Julia Equestris (Nyon) on Lake Geneva. Octodurum (Martigny) became an important administrative centre and staging post at one end of the Great St Bernard pass, and Genava (Geneva) expanded as a place where goods were transhipped from water to road.