The #1 most unforgettable experience in Greece?

I have seen the almost simultaneous July sunset and full-moonrise over the caldera of Santorini Island in the Aegean Sea. It's something you'll never forget if you're fortunate enough to be there when it happens (July).

If you're male, a unique experience is hiking and staying in monasteries on Mount Athos.

I've not yet that much experiences in Greece, but the one which will come always in my mind is
the "end of School"-Trip we made with our class of 13 People, which was organised be the only two
females in the class and we went to Mykonos!

Then after arriving 10 of us regognised that Mykonos was the "Gay"-Island (the eleventh male knew of it because he was gay). But it was not as bad as expected and we had a great loughter and great fun.
(That was a time before Wikipedia and the knowledge of the WWW in 1996)

No hidden spots or areas not mentioned on main sites, but my top three are:

• Being thrown out of a Meteora monastery by a monk for reasons I still cannot fathom.
• Hitchhiking with four fellow travellers (all girls except me and always in one car) across the mainland to Delphi.
• Staying at an ultra-luxury resort on an island for a week almost for free.

All of that was entirely unplanned.

A night spent in Athens bus station is high up there on the 'worst night of my life' list - hitch hiking from UK to Cyprus(and back), summer 1980.

Ios, summer of 1986; now, that was a party... We tried for 5 days in a row to catch a boat back to Piraeus, but in those days the only ferry was at 8 am and at that time we always were sound asleep...
Eating kalamarakia on the beach across the road from the old Athens airport.
More eating while watching the sun set from a caldera view terrace in Fira, Santorini.
Having a discussion on politics and life in general with local elderly men (my Greek is very limited) on a kafenio terrace in Crete.
My first nude beach experience, haha.
Arriving at 6.30am at Epidaurus theatre and having the place to yourself.
But apart from the people, nature, monuments and food, the thing that probably attracts me the most in Greece is the light. Nowhere in Europe the light is as bright as in Greece. And sunrises and sunsets are spectacular.

If I only could pick one place, I would visit the Acropolis.

You are looking for more than one place, dont you ?

Road tripping. Greece is perfect for road trips...the dramatic landscape and coastline are never boring. You got mountains, you got beaches, you got coves, you got caves, you got waterfalls, you got ruins of medieval castles and forts that you run into often...and you're never far from a bite to eat. You've got everything in a single road trip.

The unspoilt sandy beaches of (car free) Gavdos Island.