Depicted are the routes ferry companies use to travel between the islands of the Northern Cyclades and the mainland.
Ferry boats of various types, speeds and sizes arrive and depart from both Piraeus main harbor and Athens tertiary harbor of Rafina all year long.
They do so with much greater frequency in high summer when there may be 6 boats a day from Piraeus and two to three from Rafina. In general Piraeus is always the safer bet as its the bigger and far busier port.
Syros is the capital of the Cyclades and while it may not be quite as popular as Paros or Mykonos, it is the island you will typically need to get to in order to transfer from the northern cycladic chain to a southern, eastern or even western Cycladic island.
From Syros you can also jump the island group barrier and leap to Ikaria in the Dodecanese when such boats are available. If its Syros you want visit first, then depart from Piraeus and it will be a direct trip. Leave from Rafina and it will be way down the line if at all. Routes vary with different ferry boats companies as do vessel size, speed and cost.
Mykonos and Delos are the most popular islands of this group. Delos has no direct service from either Piraeus or Rafina and is most easily, cheaply and frequently reached from Mykonos although in high summer the occasional day boat from Naxos or Paros will make the trip albeit at much higher cost. (40 eu vs. 8 eu for example)
Northernmost Andros is off the beaten track for most short duration foreign visitors but popular with Greeks who can afford to get away from their fellows there. Tinos receives a steady number of passengers for religious reasons, as it is home to the most sacred shrine of the Orthodox church in Greece and you will likely pass by this island almost as often as Syros.
In general these islands are very well served by ferry boats but they also receive the brunt of the meltemi wind.
Ferry Costs, Ferry Schedule Chart, Note about FS, Ferry Operators, Piraeus Port, Going to Turkey, Greek Islands Map, Beaufort Wind Scale, C. Cyclades Routes, E. Cyclades Routes, N. Cyclades Routes, W. Cyclades Routes, Ferry Gallery 1, Ferry Gallery 2, Ferry Gallery 3, Ferry Gallery 4, Ferry Gallery 5.