The availability of a cabin is visible on the cabin website calendar.
Red = booked until noon next day
White = available from 2 pm 

Or in the online-booking system:
See in just couple of minutes if there are available cabins. No registration is needed and viewing available cabins does not require a reservation either. However, if you do find a cabin that meets your needs, you’ll save 13 € when you make an online booking.

Online-reservation

Please note: some cabins are sold in fixed periods. For more info, read “Useful information for cabins”.