Before you enter the campsite, you will see a meadow strip on the left hand side next to the road.
There you will find a parking lot reserved exclusively for you. 

Then go past the building to your left (reception/restaurant/washhouse) on the right  side of the building, until you see a meadow to your left. You'll see the house standing on it. 

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You don't have to register at the campsite. Just go to the house and open the keylock and off you go. 

 

 

Get the key from Keylock: 

As soon as you're standing in front of the back of the house (where the drawbar is), you'll find a black box on the pile of wood to the right of the kitchen window - the key safe. 
Enter Keylock 1627 and pull down the "lever" to the left of the numbers. Et voilà!