I don’t understand this sentence well. That means there is something interesting in the sewer?
It’s difficult to say without knowing the context of this phrase. Just at face value, I’d explain it like this: The main thing people notice about sewers is the smell (what meets the nose). However, they are saying that there is more about the sewers than just the smell. I am hoping you’ll reply with the context, however, because this may have just been figurative language.