The Olza is a river in Cieszyn Silesia, a right-bank tributary of the Oder, flowing along the Polish–Czech border. The app was created as part of the ‘Wędrówki doliną Olzy’ (Walks along the Olza Valley) project, carried out by the Hażlach municipality together with the Muzeum Těšínska in Český Těšín, which runs the Archeopark in Chotěbuz-Podobora. We created a mobile app for Android and iOS phones that works as an audio guide to the Olza valley. The recordings let visitors explore the area at their own pace, with their phone in hand. The app is available in Polish, English and Czech.