Although it belongs to the administrative region of West Greece, Achaia is on the territory of Peloponnese, in the northwest part. Its capital town is Patra, which is also the largest city on the peninsula. Next to Patra is the bridge of Rio Antirrio which connects Peloponnese with mainland Greece over the narrowest part of Patras Gulf.
The most interesting sight in Achaia is the Cave of the Lakes. It is a cave with cascading lakes on three levels, near the town of Kalavryta.