Abstract: In this paper, we describe a prototype of an adaptive indoor navigation system which is based on mobile devices and navigates visually impaired people through an unknown building. The system determines the users position inside the building on the basis of a map of the building with the help of Bluetooth-beacons. Since an exact navigation is necessary for navigating visually impaired people, we show how the system uses landmarks for gaining a higher precision for the navigation instructions for the users. We show how the system is able to determine the maximal achievable accuracy in localizing users in the given infrastructure and how the system adapts the navigation to the accuracy.