Naxos and Syros are only about 30 nautical miles apart, roughly 56 km, yet this is one of the less obvious links in the Cyclades. It connects Naxos, with its long beaches and mountain villages, with the capital of the whole archipelago, and it is handy for anyone heading north towards Tinos, Andros or the western islands after time on Naxos.
Syros has the largest population in the Cyclades and a real town at its heart: Ermoupoli, with its neoclassical squares and a working harbour that stays busy all year. After Naxos, it makes a change of pace, with more of a town feel and easy onward connections to Piraeus and the northern islands.
How you travel depends on when you go. In the warmer months, Seajets runs high-speed boats that take a little over an hour, several days a week and every day in some months. Blue Star Ferries keeps the route going all year, but only on one or two days a week in Ferryhopper's data, and its crossing can take up to 3 hr 10 min because the ship calls at other islands on the way.
The price gap is striking. Blue Star started at €8.50 when we checked, while Seajets started at €59.70. If you have a flexible day and do not mind a longer trip, the conventional ship is by far the cheaper choice; if you are short of time, the catamaran saves one to two hours.