Đavolja varoš (Devil's Town) is a place in Serbia I've wanted to visit for a very long time. And the first weekend in October, I finally did. The main attraction are breathtaking stone formations, but everything around the place is unusual and beautiful: the "red river" flowing nearby, the twisted and crooked trees, and the formations themselves, of course.
You can read more about the place here: http://www.serbia.com/visit-serbia/natural-beauties/unique-nature/djavolja-varos-devils-town/
Other than Devil's Town, I used the weekend to wander around the surrounding mountains and forests, and it was a good choice. The nature in this area is almost intact.