Ventotene be reached from Formia with ferry and hydrofoil all year and in the summer also from Naples by Hydrofoil

By car you can get FreeWay Payment or provincial road, it take the same time. you wil need the same attention to the speed camera and autovelox

By train from Rome or Naples to Formia time is less. From the train Station to the Peer it takes 10 minutes by foot or taxi which takes 5 minutes.