Three days in Istanbul is tight but workable if you accept that you cannot do both the monuments and the neighbourhoods properly and choose a split in advance. The useful division is one day in the historic core, one on the Asian side, and one on the Bosphorus. Anyone who can find Istanbul flight deals on Traveloka should also book the two ticketed sights before arriving, because the queues are the real constraint.
Day one, early: Hagia Sophia and the Blue Mosque
Both are working mosques now, which means free entry and closures around the five daily prayers. Hagia Sophia at opening is the only time it is not shoulder to shoulder. The Blue Mosque across the park takes twenty minutes. Women need a headscarf, available at the door, and everyone needs covered knees and shoes in hand.
Day one, later: the Basilica Cistern and Topkapi
The sixth-century cistern beneath the square has been relit theatrically and is cooler than anywhere above ground. Topkapi needs two hours minimum, and the Harem is a separate ticket worth buying. If time runs short, skip the palace and take the Archaeological Museum instead, which is less crowded and holds the Alexander sarcophagus.
Day two: the Asian side
Take the ferry from Eminonu to Kadikoy for twenty minutes of gulls and tea, then spend the morning in the market streets behind the pier, which is where the city actually eats. Walk north to Moda for the waterfront, or take a short bus to Kuzguncuk for the timber houses. No monuments, which is the point.
Day three: up the Bosphorus
The public ferry runs from Eminonu to Anadolu Kavagi near the Black Sea mouth and back, taking most of a day for the price of a bus fare. It stops at Besiktas, Kanlica and Sariyer. Get off at Kanlica for yoghurt and the view, or stay on and treat the whole thing as a cheap cruise.
The Grand Bazaar, briefly
Four thousand shops under one roof, and the first two hundred metres from any gate sell the same things at the highest prices. Walk deeper for the jewellers’ and carpet sections, or go to the Spice Bazaar near the ferry terminal instead, which is smaller and more useful. Both close Sundays.
Eating without ending up in a tourist trap
Avoid anywhere with a photo menu or a man outside inviting you in, which covers most of Sultanahmet. Walk ten minutes to Kumkapi for fish, or across to Karakoy for the better modern restaurants. A balik ekmek fish sandwich from the boats at Eminonu is the cheapest decent meal in the city.
An Istanbulkart covers ferries, trams, buses and the metro. Tram T1 links the airport metro to Sultanahmet. April to June and September to October are best. Traveloka offers the lowest flight prices in the region, and staying in Karakoy or Beyoglu rather than Sultanahmet puts you nearer the food and the ferries.
Book the monuments ahead, cross to Asia on day two, and spend day three on a public ferry. Three days done that way does not feel rushed.