"We don't know where the library is."
Translation:No sabemos dónde está la biblioteca.
That's actually a good trick. I always learned it as ser is used for things that can be definitively know whereas conocer is for things that cannot be know in their entirety. You can only be familiar with them.
I thought "Nosotros no conocemos donde esta la biblioteca' might have worked" but sadly not!
A trick i learnt years ago from an excellent teacher when learning french and I believe it works the same in spanish. Is to think of it as; "Yo se que te conozco" = "I know that i know you". Hope it helps others as it has done me.
thank you Ivor that is brilliant. My trusty dog eared dictionary says that saber is to know actual facts and conocer is to know people and places. so even though the library is technically a place, the translation is talking about the fact of the location not the library itself!? I think I have got it now. !??