Epidaurus is an ancient sanctuary and theatre site on the eastern Peloponnese, about 30 kilometres east of Nafplio. The theatre is the reason most people come, and it deserves its reputation: built in the fourth century BC, it seats 14,000 people and has acoustics so precise that a coin dropped on the stage can be heard in the back row. It is the best-preserved ancient Greek theatre in existence and is still used for performances during the Athens and Epidaurus Festival every summer (July and August).
The wider archaeological site was a healing sanctuary dedicated to Asklepios, the god of medicine. Patients came from across the Greek world to be cured — the treatment involved sleeping in a sacred dormitory and receiving the god's instructions in a dream. The remains include temples, a gymnasium, and a tholos (circular building) whose purpose is still debated. The site museum has a good collection of surgical instruments, architectural fragments, and stone tablets recording miraculous cures.
Epidaurus is most easily visited as a day trip from Nafplio, which is the better base for exploring the eastern Peloponnese.