Istanbul

Istanbul is a city of sixteen million people, and that scale changes how you should read its crowd data. Galataport takes large cruise ships directly at Karaköy, but a few thousand passengers disappear into a metropolis of this size in a way they never could in Dubrovnik or Santorini — the queues at Hagia Sophia and the Topkapı are set by the general visitor season, not by the ship board. What does concentrate is geography: almost everything on a first visit sits inside the Sultanahmet peninsula, and that square kilometre carries the whole load.

The seasonal shape is a double shoulder peak. April and May are the strongest months — mild, dry-ish, with the tulip planting in Emirgan and Gülhane at its height and the Bosphorus finally warm enough to sit outside. September and October are their equal or better, with the summer humidity gone and the light on the water at its best. Between them sits a July and August dip: 29°C combined with high humidity is genuinely unpleasant, many Istanbullus leave for the Aegean coast, and the queues get shorter as a result.

Winter is the real off-peak and it is wetter and colder than most visitors expect — 9°C, thirteen rain days, and occasional snow on the domes. In exchange you get the Basilica Cistern without a wait and the Grand Bazaar at a pace where haggling is actually possible. One movable factor overrides all of this: Ramadan and the Eid holidays shift back around eleven days each year, and both change the rhythm of the city considerably — iftar crowds fill the Sultanahmet park at sunset, and many families travel during Eid.