We have a huge camphor tree in the center of the yard and I swear it has roots creeping under the entire plot. I've yet to dig somewhere where I haven't needed Paul to come along eventually and whack up a monster root so it's out of my way. Sometimes even he gives up on it -- they're so gnarly.
It's a pleasant smell though -- when you dig and hit a camphor root. Kind of medicine-y but kind of spicy too.