The Crystal Cruise ship's terminal can be found on the point of the Istanbul strait (Bosphorus) near the Galata Tower. This point of the Istanbul Strait is where the Golden Horn inlet flows into the Bosphorus and Sea of Marmara. Another landmark that will assist you in finding the cruise port terminal is the Galata Bridge. It sits directly between the cruise terminal on the Galata Tower side and Eminönü on the opposite side of the Golden Horn.
For more info, see our feature Istanbul Port FAQ