The Valens Aqueduct
The Calens Aqueduct, also known as Bozdogan Kemeri in Turkish, was constructed by emperor valens in the fourth century and has been supplying water to istanbul for 15 centuries, through the roman, byzantine, and ottoman eras. you may still visit the aqueduct, the majority of which is still standing despite being only 50 meters shorter than it was originally. here is all you need to know about it if you're interested in doing it.