If you had one suggestion... one must do... what would it be?

For me, Santorini was mostly about chilling out, walks along the footpaths--it's possible to walk from Thira to Oia, mostly on footpaths. For me, the one "must do" would be to go to the Minoan excavation of Akrotiri south of Thira, but I think I read on some thread that is was closed, which is a pity.

If you can arrange to be there for a full moon, watch the moon rise over the island from a good vantage point in Oia. If you aren't going to be there at that time, make a point of getting up early to watch the sunrise from someplace high up that faces east. For the sunset, go to Oia and walk out past the desalination plant to the beginning of the hiking trail between Oia and Fira. You'll be up higher than the village and will have a great view from there AND it won't be crowded.

I suggest renting a car (a jeep or Smart Car is fun) to explore the island. The lowlands give a contrasting perspective to the caldera views ... the boats, little churches, local grocery stores. All of Santorini is gorgeous.

Akrotiri was closed in Sept. 2005 when the protective roof collaspsed killing and injuring several tourists.
Make sure you go down to Amoudi Harbor for lunch.

I didn't know what had happened at Akrotiri--it was enclosed under a stort of shed-like tin roof if I remember. That's very sad.

Cathinjoe -- The old roof was not the problem, at akrotiri! They were putting up a NEW ceiling, with a different kind of support (more aesthetic, less obtrusive), and that was their downfall. I don't know how it is being solved -- all I know is that the re-opening keeps being pushed back.

bookmarking for my "empty nest" trip! (still a few years away)

It's taken them until now to come up with a workable plan for the new roof. It's now in the hands of the local "planning commission" to evaluate the plan and give the go-ahead so the rebuilding can begin. But who knows how long it's going to take for the approval, let alone the actual reconstruction.

colin - thanks for starting this thread - I'll be in Santorini for 5 days in September.

If I come across anything I'll post...

i loved the walk from thira to oia
and i dont think it was a 'hike'
i did it in flip flops
thick soled mind you but still very doable for anyone of even average fitness
no steep climbs really
wouldnt do it without a guy though...a bit isolated at times but never spooky

Just enjoy the scenery and definitely go to Ammoudi for fish at Katinas.

Browse the little shops and enjoy the sunsets with a cool one in hand.

Relax, relax, relax, its all SO beautiful!!!!!!!!!

2 special things:

1) Grab some Greek food & wine from a local market and have a picnic overlooking the caldera - we did this on our balcony at Esperas in Oia - had some wine, grape leaves, olives, feta cheese, tomatoes, etc. and just enjoyed the spectacular view

2) if you can afford it, do a catamaran trip with Captain Ted from Santorinisailing.com - he's been featured on Giada in Paradise, the Travel Channel and CBS - beautiful and more private way to experience sailing in the caldera - you visit the hot springs, have a delicious lunch, wine, etc. and you get to see the Santorini coastline - Red Beach, White Beach, Nea Kameni, Palea Kameni - spectacular way to spend the day. We spent 135E per person for a half day trip on the Blue Lagoon catamaran - there were about 8 other people on the boat with us and it was a pretty intimate setting. It is a bit expensive (especially with the exchange rate), but we decided to splurge and we are glad we did! You can do full day trips and private excursions as well which are obviously more expensive...

Oh yes, and definitely Amoudi! The water and little boats in that area are beautiful...