Day-Tripper

Yesterday we went to Yoros Castle and Sile (that should be spelled with a Turkish "shay," but they don't print in this system). Sile is a little seaside town only a hour away from Istanbul. Its like a Turkish version of the Jersey shore; it's a working seaport with middle-class amenities, but it's pretty and we enjoyed the visit. That oe-hour drive seems to be a good road-trip distance with three little kids. Does anyone have other suggestions for places that kids would like within an hour or two of Istanbul?