Greece divides cleanly between the mainland and the islands, and the two require different planning. Athens and Thessaloniki are year-round cities with ancient and Byzantine layers; the islands — Rhodes, Corfu, Crete and the rest — run on ferry and flight schedules that thin out sharply outside summer.
The guides on this page cover Athens, Thessaloniki, Rhodes, Corfu and other destinations. For island trips, ferry timetables are the real constraint: routes are frequent from June to September and reduced or suspended in winter, so island-hopping plans should be built around sailings rather than the other way round. On the mainland, spring and autumn are better for archaeological sites, where shade is scarce and midsummer afternoons are punishing.