The largest fortress in Europe is the Belgrade Fortress, located in Belgrade, Serbia. This historical complex overlooks the confluence of the River Sava and the Danube and has existed in various forms since the 1st century AD. The fortress consists of a series of walls, towers, and gates built over centuries, reflecting Roman, Byzantine, Ottoman, and Austro-Hungarian architectural styles. It serves as an important cultural and historical site, attracting tourists with its extensive grounds, picturesque views, and rich history, including roles in various military conflicts throughout the centuries.