Shall I tell you about Evvia which is only 1 hour from Athens? If you flew into the airport and picked up a hire car then you’d get to the port of Rafina in about 30 minutes and then one hour later you’d be driving off the ferry into Marmari and you’ve got the coast road to Karystos which is as good a place as any to spend your first night before deciding whether to spend a few days driving around the island and staying in a different place each evening or to find the beaches further out on the peninsula that, even in August, are so quiet that you drift into that lazy, dazed holiday state and before you know it you need an hourly nap. Watching the ocean really takes it out of you.
If you wanted an island larger than Agistri and were happy to drive in Greece then think about Evvia. If you’re a hiker then Evvia’s worth a visit in the spring or the autumn although I would favour the spring, especially before May. If you walk in March or April then you’ll get some sunshine without the high temperatures and the beautiful spring flowers will lend some colour to the landscape. After the summer the mountains will look dryer and rougher but you still have those fantastic views across the Saronic Gulf and the bonus of the sea staying warm enough to swim in until October. In fairness, I wouldn’t want to confuse any Californians who might find this and would add that the sea is only warm enough if you’re from Northern Europe. The Greeks will be in woolly hats by October.