If you are wheel chair bound it is recommend not going to Istanbul. It is hilly and where it is not the streets are cobbled and with ruts and ridges pavements with no ramp. Even where disabled access within a building is mentioned - practically it is useless as entry into some of the highlighted touristr attractions eg the Old City is impossible to get through. Further more attempting to get help was dreadful - generally disbled people are taken advantage of and ripped of by operator and taxis charging extras upfront and otherwise - watch out for the taxi meter which could be running from someone else's ride.

The Istanbul Forum, supposed to be disability friendly had lifts that had lengthy queues and were slow and small.

Considering how much money is taken from tourists and how much tourism is clearly a  great money spinner more should be spent on visiotrs with difficulties, especially since Turkey wants to be part of the EEC