Lisbon, Malta and Istanbul are all rather hilly - not so easy for pushing a pram around or keeping the toddler from getting tired when walking. Public transportation options aren't great either, especially for those like me who don't want to carry a car seat around and/or just hop in the back seat of a taxi without one.

Stick to places with reliable public transportation options and activities for children - Berlin, Vienna, London, Paris, Amsterdam, etc.