Formia to Siderno trains might be a good value for money solution: travelling in Italy by train is often rather cheap and faster than taking a bus indeed Trains leave from Formia-Gaeta and arrive at Siderno every about 6 hours on average. If travelling with Trenitalia, you need to know the Formia to Siderno train schedule: the first train leaves at 23:40, while the last ride is at 23:40. A Formia to Siderno train cost about 56.4 €. But how long is the train ride from Formia to Siderno? Your journey takes about 9 hours on average.