Undeservedly little known to many people, the site of Epidaurus is really one of the nicest and most interesting places to visit in Greece. The amphitheatre boasts great acoustics and is one of the best preserved ancient sites anywhere, and the rest of the archaeological area is very interesting as well, especially when you hear about the history of Epidauros as a kind of ancient spa and medical resort that featured hotels, hospitals, and bathrooms. The museum is pretty small, but has some interesting artifacts. The place is only about two hours from Athens and can easily be combined with trips to places like Corinth and Mykene.