Along unpaved roads see the post soviet industrial decay amidst mountain villages. In Berat (Unesco) marvel at the architecture and friendly people. Old Town Tirana has some heritage 'hotels'. Visit Krujë Castle Museum. Take an unforgetable and scary trip down the mountain side to Theth NP only suitable for 4WD Jeeps (carefully driven 2WD hire cars).
See the famous Stari Most and old town in Mostar and close by the Dervish House in Blagaj. Enjoy the bustling old quarters of Saravejo. Driving from South to North you will pass by wild uplands, maybe a chinese town being built, many mosques and exit through orthodox Бања Лука - Banja Luka
In Sofia, a very walkable and friendly city, you cannot miss Alexander Nevsky Cathedral (Свети Александър Невски) - all around are many notable buildings and an art market . From Sofia it is a day trip by car to century Rila Monastry (Рилски манастир) and back via the ski lifts for the mountain views.
Has everything: Ferries to the islands, Beaches, Roman ruins, Mountains, Risnnjak, Krka and Plitvice National Parks, Split and Dubrovnok aka Kings Landing. But also Zagreb, Slavonia and Naive Art.
Kosovo is welcoming and safe, an easy drive in from Macedonia, but do not attempt from Serbia. Pristina has a surprising European late 60's feel and a maze of narrow streets as you enter the bazaar district. The highlight was the drive from Prizren, itself a very photographic city, across the mountain roads back to Blace on the border.
Disneyesque Skopje (Скопје) is a fun city. Cross the Kameni Most and you will find the Čaršija turkish bazaar. Going south, drive through Mariovo NP with its deep river canyons and mountains. This will take you to picturesque Ohrid (Охрид) with its lake, fortress, theatre and the famous churches of Sveti Jovan and, St. Clement and St. Panteleimon.
Podgorica has brutalist architecture, but a nice cathedral. Kotor is a gem, eclectic hotels, old city and climb to the fort. Drive to along the coast, see Sveti Stevan, to Virpazar and then the single track to Rijeka Crnojevica for lunch, see the river bends and then to Bijelosi and through Lovćen NP to the 32 hairpins back down to Kotor.
Explore along the Danube and Sava rivers, take in the views from Belgrade Fortress, enjoy the Street Art and eat in Skadarlija St., I enjoyed Niš and Devil's Town (Đavolja Varoš) in the South and the little visited Lepenski Vir museum in the North. Tara and Đerdap National Parks have great views.
Don't forget to have 'Breakfast in Bled' and then walk the Vintgar Gorge. Explore the wonderful capital of Ljubljana with its fortress, Baroque and Art Noveau buildings and the casual cafe and market life along the river. Take a look at the Street Art around Metelkova. Triglav National Park has awesome views.