Hidden high in a rugged mountain valley, 34km northwest of Antalya, lies the ruined but still massive ancient city of Termessos. Neither Greek nor Lycian, the inhabitants were Pisidian, fierce and prone to warring. They successfully fought off Alexander the Great in 333 BC, and the Romans (perhaps wisely) accepted Termessos' wishes to remain independent and an ally in 70 BC. It's a fairly tough 150m hike over rocky terrain to the upper city, so good footwear is essential.
In the car park, at the end of the Termessos access road (King's Rd), you come across the lower city ruins. The portal on the hillock to the west was once the entrance to the Artemis-Hadrian Temple and Hadrian Propylaeum. From here follow the steep path south; you'll see remains of the lower city walls on both sides and pass through the city gate before reaching, in about 20 minutes, the lower gymnasium and baths on your left.
A short distance uphill from the lower city ruins are the remnants of Termessos' upper city walls and a colonnaded street. Just above is the upper agora and its five large cisterns, an ideal spot to explore slowly and to catch some shade.
On the eastern side of the upper agora is the theatre, which enjoys a positively jaw-dropping position atop a peak, surrounded by a mountain range; you can see Antalya on a clear day. Walk southwest from the theatre to view the cut-limestone bouleuterion, but use caution when scrambling across the crumbled Temple of Artemis and Temple of Zeus to the south.
Termessos' southern necropolis is at the very top of the valley, 3km (one hour's walk) up from the car park at the site entrance.
The site is spread out and requires much scrambling over loose rocks and up steep, though well-marked, paths. Allow a minimum of two hours to explore and bring plenty of drinking water.
Taxi tours from Antalya cost around €50, or you could take an organised excursion for less. A cheaper option is to catch a bus from Antalya otogar bound for Korkuteli (₺12) and alight at the entrance to Güllükdağı Termessos National Park. Taxis waiting here in the warmer months will run you up the 9km-long King's Rd to the ruins and back. The fare should be about ₺30, but you will have to negotiate.