Istanbul Metro

Istanbul is too big for one transit trick. The metro is very useful, but it is not the whole answer. Use it for long jumps, airport approaches, and the newer business/residential city. Use the tram, ferries, and walking for the old city and Bosphorus version of the trip.

How I would use it

For Istanbul Airport, M11 is now the rail answer. It is fast once you are on it, but the trip can still be a chain of transfers depending on where you sleep. If you are aiming at Taksim, Beyoğlu, Şişli, Levent, or another M2-adjacent stay, the Gayrettepe connection matters. If you are aiming at Sultanahmet, you still need to think through the last leg.

For Sabiha Gökçen, M4 is the practical line. It gets you to Kadıköy, and from there you can decide whether the ferry, Marmaray, or another metro leg makes sense. It is not a single-seat ride to the old city.

Payment

Use Istanbulkart if you like having a stored-value transit card. For a short visit, contactless also works on public transport according to the city tourism office. The practical rule is the same as London: use the same card or phone wallet, and do not switch devices mid-trip because the system reads those as different cards.

Built-environment note

Istanbul's transit story is the geography. The city is split by water, hills, the Bosphorus, the Golden Horn, and two airports that sit far apart. That is why the system feels like layers rather than one tidy metro map.

The interesting part is the contrast: old-city movement still belongs to T1, ferries, and walking, while the modern metro keeps punching deep tunnels through the harder city around it. M11 is the extreme version: a long airport metro that makes sense because the airport is so far from the historic center.