Things to see in Belgrade

What I remember from my one day trip to Belgrade is the Kalemegdan Citadel with its fortifications, the Stari Grad(the old city), the Skadarske cemetery where you can get a glimpse of Serbia's past , the biggest Orthodox Church in the world the Sveti Sava, to name just a few. I also went to a couple of museums, the most interesting being the Gallery of Frescoes with real size replicas of the most important religious paintings, and the National Museum.