Hell was going to be my guess too. But then I thought “well, he hasn’t been to heaven either…” And that would be two places he hasn’t been. But I’m probably overthinking it.
Hank Snow made it a #1 hit in the USA; Cash covered it later on. It has a different ending, also, with the backup singers singing the line “I know someplace you haven’t been.” and Snow replying “I have been everywhere.”
I just listened to the Stompin’ Tom version of the song. The way he ends it makes me think that the one place he hasn’t been is the exact place he is hitching to.
Having just listened to Lucky Starr’s original, the tag line in the OP is given by the man who stopped to give the singer a ride.
I think the intention, given the song was written for an Australian audience and from the way the driver said the line, he was telling him to go to buggery [traditional Australian idiom - ‘hell’ or even ‘heck’ will probably get you half points].
And checking the lyrics, on a rough count there are 94 place names mentioned, and I’m pretty sure I’ve been to 47, so exactly half. Could become a good retirement project.
Well, he’s been under the big sun of Mercury, visited the oceans of Venus, fought the pirates of the asteroids, walked the moons of Jupiter and touched the rings of Saturn. So… Uranus?
Oh I’ve been to Nice and the isle of Greece
While I sipped champagne on a yacht
I moved like Harlow in Monte Carlo and showed 'em what I’ve got
I’ve been undressed by kings and I’ve seen some things
That a woman ain’t s’posed to see
I’ve been to paradise, but I’ve never been to me