Folegandros to Sifnos links two of the most loved small islands of the western Cyclades. Folegandros is all cliffs and silence, with a Chora perched high above the sea and a coast you mostly reach on foot or by small boat. Sifnos is softer and greener, a walker's and food lover's island of whitewashed villages, monasteries and pottery workshops, with Apollonia at its heart and Kamares as its port.
The route is a handy piece of the western island chain. Many travellers come down from Piraeus through Serifos and Sifnos to Milos and Folegandros and then turn north again, or do it the other way round; this crossing lets you skip Milos and go straight between the two quieter islands. It also connects Folegandros, which has no airport, with a port that has frequent boats to Piraeus.
The surprising thing about this route is that the slow boat is not always slow. In Ferryhopper's table of last year's sailings, Fast Ferries' conventional ship took between 1 hr 35 min and 2 hr 10 min, while the Seajets high-speed boats took about 1 hr 55 min. Since Fast Ferries started at €8 and Seajets at €57.70, most people on a budget will not hesitate.
The catch is frequency. Fast Ferries sails three to five days a week, and Seajets only between March and November, so look up your date before you commit to rooms on either island, and build in a spare day if Sifnos is your step towards a flight from Athens.