In reply to 01wills:
Coming FROM Serbia your best bet for sport climbing in Romania is Herculane. You can see an online topo here:
http://climbingtopo.ro/area.php?area_name=Herculane
Climbing in Romania there is galore - mainly limestone but also conglomerate. Sport and multipitch, bolted and adventure. There is also some bouldering, quite OK, but fairly obscure and not easy to find if not familiar with the lay of the land
We are offering guiding services as well as climbing courses. Check us out on
http://www.alpine-style.info and get in touch at contact@alpine-style.info if we can be of help or if you would like to book one of our guides.
For Turkey the weather is def way too hot now to make climbing bearable in the major destinations (like Olympos and Antalya). They are 1k km SE of Istanbul anyway... Your best bet would be Ala Daglar National Park which is high up and cooler but still further E/SE from Istanbul.
Now, if you are driving FROM Istanbul towards W the I suggest you follow the highway all the way to the Bulgarian border through Edirne (Turkey) to Svilengrad (Bulgaria) and up to Veliko Turnovo (sweet climbing spot). Check out in town (town centre, up on a cobble stone road from the little fountain ) a nice British owned B&B and you cna get topo and crag informations from there. sport / bolted. Eat well at 'Tempo" pizza downtown and they have wifi as well
Follow then up north into Romania through Ruse (BG) - Giurgiu (RO) border -- bypass Bucharest unless you plan on having a city break (big, buzy, torrid) and head up north o Sinaia - Busteni (DN1 - National road no 1). Stop in Busteni - multi pitch bolted and adventure climbs from 100m to 500m on conglomerate - loads. You can camp or use one of the gazillion B&Bs. Free hut available but tricky to find if not familiar with the place. Good hiking opportunities.
From Busteni you have several options: up North in the heart of Transilvania Turzii Gorge (sport single and multi pitch on limestone - easy access, short walk in, cheap campsite) then E to Vadul Crisului (similar as Turzii Gorge) then south towards Herculane (see link above) then out into Serbia to Croatia (Paclenika probably too hot) then into Slovenia which i highly recommed. In Slovenia at this time of the year i would recommend Kotecnik crag (near Kranj) and for multi pitch Vezica (in the Kamnik Alps). A new guidebook just came out (last month) for sport climbing in Slovenia and is excellent on all accounts.
Exit Slovenia through Maribor (n highway) and carry on towards Budapest then up to Czeck Republic and Poland.... there is lots tehre but am sure you have that figured out.
Happy climbing!
C