If you consider visiting Van, I recommend you to take train. This route is still not popular enough among tourists because eastern Turkey had gone through violent conflicts. As long as you don’t get yourself in trouble intentionally, you’ll be safe though. I traveled Eastern Turkey by hitchhiking last year with my wife, and felt really safe and welcomed. People are very friendly, food is great, the nature is like Switzerland. I’m sure that this area will be too touristic to visit in the future, so I recommend you see there before it gets hit by tourism.
If you want to do a full trip in Turkey, this is my route recommendation: İstanbul -> flight -> Cappadocia -> Bus or hitchhike -> Urfa -> Mardin -> Hasankeyf -> Van -> Doğubeyazıt —> İran. These towns are all wonderful, and probably the most different beauties I’ve ever seen. Highly recommended.