Download the Ahoi Bollwerk 21 app to book your courses yourself. The courses differ between play courses, baby and children's swimming, childcare hours in the playgroup and courses related to pregnancy. The app shows you our course schedules and their availability so that you can register for courses. The Ahoi Bollwerk 21 app contains our location and contact information. Optimize your balance between family, free time and work and save time with our app.