Now entering its 66th year, the Summer on the Vrbas festival is one of the biggest summer celebrations in the city. Banja Luka is built around the Vrbas river, so paying homage to that great body of water seems like an appropriate move. The event takes place over seven days in July and features a mass of activities, both sporting and cultural, along with huge amounts of food, drink and the rest. There is also a zip line next to the fortress every day between 17:00 until 20:00, for the adrenaline junkies out there.