You tube if you want to...

Travelling through Germany, I happened across this sign in the hotel bathroom.

Can you spot the mistake?

While I confess that I am a stickler for good spelling and grammar, I am more understanding if the final message is clear enough.   However, I would point out an error if it leads to a different meaning or if it's just plain nonsense.

So I followed the sign to the letter and I placed my towel "in the bath-tube" (or technically speaking, on the shower tube).

I politely pointed this out at the reception as a helpful suggestion and added, "By the way, I'm a translator. Here are my contact details - you never know when you might need one."
The receptionist seemed slightly bemused, laughing nervously but thankful.

And who knows, while a business deal would be a plus, I feel that I have helped the English-speaking hotel guest with that first-world problem of where to put the used bath towel if it needs to be washed.