If you decide to go on holiday to Serbia, I would strongly recommend Tours from Belgrade. I found out about this company from TripAdvisor reviews, contacted them and got a response on the same day. Since I had just 4 days, I really wanted to see as much as I could including cultural and nature as I love hiking. Darko suggested great ideas and accustomized my itinerary to match my preferences. On the first day I had a walking tour in Belgrade with guide Nemanja, even though it was rainy, I enjoyed the tour as Nemanja shared a lot of information and overall it was a very insightful experience. On the second day I went to Eastern Serbia, visited Manasija monastery, caves, waterfalls, has a great lunch at Lisine, and then I had 2 days tour with overnight in Zlatibor, visiting Mokra Gora, ethnovillage, hiking in Tara national park and many other things. Darko even took me to Visegrad, which was not part of our original program! He is really a great guide, I didn't even feel like a tourist - it was more like visiting a friend, who loves his country and has so much to share! It was a great experience and if you haven't been to Serbia yet, add it to your travel list!