A city stay can have extensions
An Istanbul visit leaves different opportunities depending on the number of usable days. A neighbourhood excursion differs from leaving the city for a regional trip.
Match destination to time
The Princes’ Islands, Bursa and the Dardanelles represent different travel scales. Cappadocia or the Aegean require their own flight or longer ground arrangements.
Keep the return realistic
Agree actual departure and return points before adding an extension. A free Istanbul day should not become an unconfirmed distant excursion before an international flight.