River — Kastanies, northern Evros, ~2 hours from the city
The Ardas rises in the Bulgarian Rhodope Mountains and joins the Evros near the village of Kastanies, in the far north of the prefecture where Greece, Bulgaria, and Turkey meet. Its banks support a wide range of birdlife, reptiles, and fish, with wild deer recorded along the riverfront in quieter stretches.
Every summer, usually in late July, the riverbank hosts the Ardas Festival, drawing campers and day visitors from across the region for a long weekend by the water — worth timing a visit around if it lines up.
This is a genuine outer edge of what counts as a day trip from Alexandroupolis — best combined with other stops in the far north of Evros rather than visited on its own.