Went to the Cengelhan Rahmi Koc Museum near the citadel today and was very impressed. It is located in an 500 year-old caravansarai (han) which has been restored very well. Inside there are lots of model trains, cars, planes and other transport-related stuff. My little one loved it. The collection itself was not that large and my guess is that the museum in Istanbul is probably better, but the restored han itself is worth the price of admission (3TL).

Yeah, the museum here is worth of every penny (Istanbul one). They have even Submarine and Airplane (DC-3) there. Lots of cars, bikes, boats, steam engine etc...

but go early, u really need the whole day, and afterwards u can chill out in their pub (might be closed during ramazan).