I have recently visited Izmir and must say that Crown Plaza is one of the best hotels there.
There are 2 key points. The amazing view overlooking the sea and the amazing Spa. This has 2 pool (indoor and outdoor) Turkish bath, 3 different types of steam rooms and 4 different types of saunas and 3 amazing hot tubs with many different jet systems.

defiantly a place to stay at.