Step out of Turna Hotel's front door and you're already standing in the middle of the old city. That's a useful place to start, since Istanbul is not a city you finish in three days. It spans two continents, has been the capital of three empires, and somehow still adds new neighbourhoods to its "you should really see this too" list every year. So let's be honest from the start: this itinerary won't show you everything. What it will do is give you three full, well-paced days that cover the parts most first-time visitors actually come for — without the 6am-to-midnight sightseeing marathon that leaves you too tired to enjoy any of it.
Step out of Turna Hotel's front door and turn either way, and you're on Küçük Ayasofya itself, a different street than the one most visitors picture when they hear "Sultanahmet." Most people's picture of the neighbourhood is Hagia Sophia's dome, a plaza full of tour groups, and vendors calling out in six languages at once. That part is real — it exists, and it's worth seeing. But Sultanahmet is bigger than that one square, and a few streets away from it, the neighbourhood looks and sounds completely different. Küçük Ayasofya is one of those streets.
Step out of Turna Hotel and the water is a two-minute walk away in one direction. That's fitting, because both of the trips in this post start with getting on a boat. If you've got one extra day in Istanbul and you're trying to decide between a Bosphorus dinner cruise and a day trip to the Princes' Islands, the good news is you can't really pick wrong — they're both good uses of a day, just completely different ones. The bad news is they don't overlap much, so if you only have room for one, it's worth knowing what you're actually choosing between.
Step out of Turna Hotel before sunrise and the street is still dark and quiet — which is exactly when this day starts, because a day trip to Cappadocia from Istanbul is one of those things that sounds almost too ambitious to be a "day trip" at all. You're talking about a landscape hundreds of kilometres away, on the other side of the country, fitted into roughly eighteen hours. It works, but it's worth knowing exactly what that day looks like before you book it, because "long but worth it" undersells both halves of that sentence.