I took the wrong destination.
'Destinazione' — des-ti-na-TSYO-ne. Six syllables; stress on the fifth syllable.
Say this on transport when you realise you have boarded the wrong vehicle heading to an unintended destination. The sooner you realise, the easier the correction.
'Ho preso la destinazione sbagliata' — 'sbagliata' (wrong) agrees with 'destinazione' (feminine). 'Prendere' (to take) is used for taking transport in Italian: 'prendo il treno' (I take the train), 'hai preso l'autobus sbagliato' (you took the wrong bus). Very versatile verb.
Sono sul treno sbagliato.
I am on the wrong train.
Simpler statement of the same problem.
Come torno indietro?
How do I go back?
Ask for the return route.
Scendo alla prossima e cambio.
I'll get off at the next stop and change.
State your action plan.
Italian inter-city rail junctions can be confusing — several major lines converge at Padua, Bologna, and Milan. Always confirm the train destination and stopping pattern on the departure board before boarding. Trenitalia's Frecce have reserved seating, so conductor checks often catch wrong-train errors early.