Either 220/380 or 230/400. The transformers I saw looked fairly modern, so it could quite well be 230.
One boat I was traveling on had waterproof Schuko outlets labeled "220V". However, the party guys ran their sound equipment off a portable generator I think. They brought that thing from Austria in their car! We used it on a few occasions when we had beach parties at very remote locations.
My Mom says they already had 220V in Greece when she went there in 1971, only ungrounded (C) sockets back then. Travel guide from 1978 states voltage should be 220V everywhere but 110V might be encountered in very remote places that generate their own power.
All houses I saw had a 3ph feed.
Our hotel definitely had a nice way to wire the air condition. It was obviously added after the hotel was built, so they put a wall-mount unit above every window. Then they ran a long piece of 3x2.5mm2 flex stapled to the walls all across the room and plugged it into a 3way adaptor next to the door. In our room the flex wasn't long enough, so they just twisted and taped 2 pieces together.
Guess it was a pretty hot summer even for that island 'cause the streets were literally paved with empty boxes of Panasonic wall-mount AC units.