In the wider Kavala area are the archaeological sites of Amphipolis (or Amfipolis). There isn't just one site for this significant ancient city, but a few, in the same area.
One of them is the majestic Lion of Amphipolis, casually just standing by the side of the road, so you can't really miss it. Obviously no entrance fee for this one, but definitely worth a stop when visiting the area.

Erected during the 4th century BC, the Lion of Amphipolis stands at 8m tall, as a symbol of honour towards Laomedon from Lesvos, a skilled seafarer fighting on Alexander the Great's side.