The Nestos Delta spreads east of Kavala where the river reaches the Aegean, creating a mix of lagoons, reed beds, riparian forest, and open water. It is one of the better nature excursions in eastern Macedonia, especially for birdwatching.
The delta rewards slow travel: a car or guided outing helps, and binoculars make a real difference. Combine it with the river gorge or nearby coastal stops if you want a fuller day outside the city.