went to istanbul 2 years ago and loved it. Now thinking of visiting somewhere else in turkey.

is there a city that anyone would recommend visiting. looking for a place with history, museums, etc

Selam, I would recommend you to see Ankara and Trabzon.

http://wikitravel.org/en/Ankara

http://wikitravel.org/en/Trabzon

There are so many others but these two are the first ones I would visit if I was you.

Or Bursa

http://en.bursa.bel.tr/

http://en.wikipedia.org/wiki/Bursa

http://www.turkeytravelplanner.com/go/ThraceMarmara/bursa/sights/sehir_merkezi.html

thank you for your help.

a difficult decision as they all look interesting.