This large patch of protected forest is on a major bird migration route and home to three of Europe's four vulture species. Visits are best in spring or in July, when baby vultures pop from their nests. The Info Centre runs a shuttle 3km in to the bird observatory, which is furnished with telescopes to spot the giant raptors feeding; the excursion takes about an hour. You can also rent a mountain bike or take an easy hike in.
Farther south, near Lefkimi, there is a patch of petrified forest that is, unlike most examples of this phenomenon, in a pleasantly shaded patch of living forest, making a nice short hike (with advance notice to the gatekeepers there; ask at the info centre). Thanks to Forest Inn, a fine guesthouse next to the park info centre, Dadia is a pleasant base for exploring the towns between Alexandroupoli and Orestiada. Of course you can drive, but for those who have time, forest trails also run to nearby villages; you can walk to Soufli in less than three hours. There are also two solid tavernas in the village of Dadia.