Regions to know
To frame your trip by what you have time for and what you're after.
Istanbul & Marmara
Istanbul, Bursa, Edirne
The gateway. Most flights land at Istanbul Airport (IST) or Sabiha Gökçen (SAW, Asian side). Stay in Sultanahmet for the monument core, or in Beyoğlu/Karaköy for trendy old buildings. The Marmara region also includes Bursa (early Ottoman capital) and Edirne (Ottoman architecture).
Cappadocia & Central Anatolia
Göreme, Üçhisar, Konya, underground cities
The 'Mars on Earth' interior. Göreme as base for the hot-air-balloon scene and cave hotels. Konya 3hr south for Sufi heritage. Fly to Kayseri (ASR) or Nevşehir (NAV) from Istanbul (1hr).
Aegean coast
Izmir, Ephesus, Pamukkale, Bodrum, Çeşme
Greek-feeling: Greek-speaking before 1923, lots of ancient Greek ruins. Izmir (IZM) is the airline hub. Pair Ephesus + Pamukkale + a coastal beach (Çeşme or Alaçatı) over 3–4 days.
Mediterranean (Turkish Riviera)
Antalya, Olympos, Fethiye, Ölüdeniz, Kalkan, Lycian Way
Beach, ancient ruins, hiking. Antalya (AYT) airport is the gateway. The Lycian Way is the long-distance hiking dream (540km, weeks); for day-hikers, day sections from Kabak or Kaş.
Black Sea
Trabzon, Sumela Monastery, Rize tea hills
Northeastern coast — cooler, wetter, greener than the rest of Turkey. Sumela Monastery clings to a cliff. Rize is the tea-growing region. Mostly Turkish tourists; few internationals.
Southeast (Gaziantep, Mardin)
Gaziantep, Mardin, Mt Nemrut, Şanlıurfa, Göbekli Tepe
Where Turkey starts looking like Mesopotamia. Gaziantep for food (baklava capital + pistachios), Mardin's stone old city overlooking the Mesopotamian plain, Göbekli Tepe (11,000 years old, oldest known temple). Less touristed; for second-trip travelers.