Belgrade is situated in the meeting point of two rivers: the Danube and the Sava. The Danube is of course the much more famous of the two, but in fact, as far as Belgrade is concerned the Sava is not less attractive.
You might think that “Sava” is a Slavic name, perhaps related to Saint Sava, the spiritual forefather of Serbia that the cathedral named after him is one of Belgrade’s most prominent buildings, but the truth is that the name of the river goes back to the time of the Roman empire. Maybe saint Sava was named after the river… I don't know…
You can take a cruise of about 90 minutes on the Sava from the pier that starts at the eastern side of the Brankov bridge and enjoy the view of the Belgrade castle and other parts of the city, from the river (the best time for this cruise would be at twilight). Then dine at one of the restaurant on the pier, like the excellent Druga Piazza. An Italian food restaurant that its owner is also an art collector, that part of his collection decorates the restaurant’s wall.
On hot days you can enjoy the watersports activities and other attractions of the Ada Cignalija island, and at night, experience the bars scene of the Sava Quay promenade, at the river’s bank, north of the Ada.