The Old Harbour of Thassos: From the olden days Thassos had two harbours - one for trading and commercial purposes and the other for military purposes. The ancient naval port is mostly referred to as old harbour and it is closed now. The foundations of round towers from the ancient harbour can still be seen on the quay.
A portion of breakwater in the sea is also preserved. Wandering around the harbour sites one comes across many archaeological sites including the ancient Agora located close by. It occupies a large area inside its walls and used to be a