Just a short drive from Fethiye, near the village of Üzümlü, is the site of Cadianda, which dates back to the 5th Century BC, though many of the structures which can be seen today would have been from the Byzantine period.
Although records suggest that it was not a particularly important city, nonetheless it had a theatre, stadium, baths, temple and agora, the remains of all of which can still be seen today.
Standing on a steep hillside around 900m above Fethiye, the city itself has an ascent of around 300m from the lower entrance. Set in pine forests, the site is very atmospheric and has fantastic views back to Fethiye.
The amphitheatre slots neatly into the hillside.
There is a footpath of sorts, but I would recommend walking boots or sturdy trainers, as the path has fallen away in places and also has some steep rocky sections.