If you want to travel to Istanbul from Kuşadası/Selcuk we recommend you do so via the beautiful Pamukkale and spend your day visiting the beautiful white terraces and the ancient ruins and take the night bus to Istanbul.
Pamukkale Tour from Kusadasi or Selcuk & Night Bus to Istanbul:
08:15 Pickup from your hotel/hostel in Kusadasi
08:45 Pickup from your hotel/hostel in Selcuk
12:00 Arrival in Pamukkale & open buffet lunch
Move on to the guided tour of the Ancient city of Hierapolis & Pamukkale:
20:00 Transfer from Pamukkale to Denizli Bus Station
21:00 Departure - Nights bus to Istanbul
Night bus from Pamukkale to Istanbul takes about 10 hours.