The Vrbas River is the best thing about Banja Luka for the outdoor-minded traveller. The river promenade (Šetalište Petra Kočića) runs along the left bank for several kilometres, lined with cafes, restaurants with terrace seating, and spots where locals swim and sunbathe on warm days. It is a genuinely pleasant riverside walk, especially in the evening when the light is good and the city's inhabitants come out to stroll.
The river itself is clean enough to swim in, and several areas with gravel beaches form unofficial swimming spots in summer. The combination of the Kastel Fortress rising from the far bank and the clear green water below makes this one of the more attractive river settings in Bosnia. Kayak rental is available near the fortress in summer for those who want to get on the water.