I am from Belgrade, capital of Serbia...It is a beautiful city and it's about 2 Million people if you include the all the small cities around it.
We have a great Ada lake, where over 1 million people come to swimming, sunbathing and other summer attractions

Ada Ciganlija is one of the most visited places in Belgrade, and for a good reason. You can go swimming, biking, rollerblading or just enjoy a walk by the lake. The place is full of bars and restaurants and most of them work all year long. During the summer it can get crowded with a seaside atmosphere.