Serbia's ancient capital has a colourful past. This place has been invaded more than 40 times, and you'll see the influence it's had on its architecture today with a guided bus and walking tour. You'll start with the city's pride and joy in Kalemegdan Park. This clifftop green space overlooks the meeting point of the Sava and Danube rivers, which made it the perfect spot for an Ottoman-era fortress. You'll walk through the pretty, riverside park and up to the ruins of Belgrade Fortress. After, you'll head for the main square, where you can gaze at a monument dedicated to Prince Mihailo, who ended the Turkish occupation in the 19th century. Then you'll stop for a drink at a nearby hotel, before ticking off Serbia's National Assembly building. Next, the bus will take you for a photo stop at the Church of Saint Sava – one of the biggest churches in the world.