Answer:
Before Google, we actually had to physically look things up in this building full of knowledge.
What is something you will never see again?
There is one in every corner and two in every room.
Without this, H2O would just be 2O
Used to keep prisoners silent and to make temporary repairs on cars.
I am the fountain from which no one can drink. For many I am considered a necessary link. Like gold to all I am sought for, but my continued death brings wealth for all to want more.