Nisyros

Nisyros is a volcanic island in the Dodecanese whose interior is an active caldera; visitors can walk on the floor of the fumarole-studded Stefanos crater. Public transport is a single municipal bus line running out and back along the island's one main road, linking Mandraki, Pali, Emporios and Nikia. It is a limited, seasonal service, so check times locally in Mandraki rather than assuming a bus.