The Istanbul Metro is still being built, but the completed lines allow you to travel easily and inexpensively between Atatürk Airport, the Otogar (main bus terminal), and the main tourist and hotel areas at Sultanahmet and Sirkeci. More...
Here's the central portion of the system, with a key to the most useful stations.
From left (west) to right (east) and top to bottom, here are notes on the most useful stations for visitors:
|— Atatürk Airport (IST)
— Otogar - Main bus terminal
The official Metro Istanbul website is in Turkish only.) Click here for a detailed map of the entire system.