Here is the neat historical trick this coast plays on you: after a day among the ruined baths of Ephesus — the Scholastica, the gymnasium suites, the harbour thermae — you can walk into a working descendant of them the same evening. The Turkish hamam is the Roman bath that refused to become archaeology.
The lineage is direct: Rome’s bathing culture passed to Byzantium, Byzantium’s to the Seljuks and Ottomans, who kept the heated marble and the social heart of it, swapped the cold plunge for running water (still religion-shaped preferences, cleanliness by flowing water), and attached the institution to every mosque complex and market town in the empire. Selçuk and Kuşadası both keep good hamams, from honest neighbourhood establishments to marble palaces built for visitors.
What actually happens
You undress, wrap in the checked cotton peştemal, and lie on the göbek taşı — the great heated marble slab under the dome — until your muscles surrender and your opinion of the day softens. Then an attendant scrubs you with the kese mitt, removing what you will be assured is an archaeological layer of skin; buries you in clouds of olive-oil soap foam worked from a lace bag; rinses you at the marble basins; and releases you, several years younger, into the cooling room for tea. Massage optional; astonishment standard.
Etiquette, briefly: swimwear or the peştemal per your comfort, sexes bathe separately or by schedule in traditional houses, tips for the scrubber are customary, and the correct amount of time to spend afterwards doing absolutely nothing is: more.
