Circumvesuviana train
Board at Napoli Porta Nolana (best chance of a seat) or Piazza Garibaldi, ride the Napoli–Sorrento line about 36 minutes, and get off at Pompei Scavi–Villa dei Misteri — 50 metres from Porta Marina. €3.30 one-way, trains every 20–30 minutes from around 5:40 am. Crowded and occasionally targeted by pickpockets, so keep bags in front of you.