Siphnos or Sifnos Island, Greece.
The Aghios Giorgios car ferry of Ventouris Lines leaves Piraeus at 7.25 am and arrives in Sifnos at 12.55 pm—daily in summer and five times weekly in winter.
This is supplemented by two late evening ferry services a week with G.A. Ferries, which continue via Milos for Santorini.
In summer only, an average of two high-speed services make the journey from Piraeus in just under three hours.
Nearly all services continue to Milos, with the larger ferries stopping at Kimolos. On the return most services stop at Serifos.