The Roman theatre at Aspendos, 47 km east of Antalya, is arguably the best-preserved theatre of the ancient world — not the largest, not the most famous, but the one whose stage building (the scaenae frons) survives almost to its full original height. Seating around 12,000 people, it is still used today for summer concerts and opera performances.
Getting there without a car requires a taxi or tour bus, but it is absolutely worth it. The theatre alone is reason enough for an afternoon excursion. Aspendos also has substantial aqueduct ruins nearby and an acropolis with forum remains. The site is open daily; the walk from the car park to the theatre is short.