It's a city of surprises. And there's Ouzo around pretty much every corner. The outdoor cinemas are amazing. The ancient buildings really are as cool as the pictures. The flea markets are definitely worth a visit - plenty of stuff you didn't know you need. The street art scene is HUGE. You might discover the next Banksy.
This is a wicked spot to start your Greek Island adventures. Most people speak good English, but Greek is a pretty beautiful language. It's a great spot for pretty much any budget. You can go as big or small as you want, so if you wanna play it fast and loose, this is a decent "last minute" vacay choice.