hockeydja is right about the tour—the best part is the cathedral, and you don’t spend nearly enough time there. I think the mine is worth visiting because there’s nothing else like it in the world and the cathedral really is stunning (even if you do only get to spend 5 minutes there). However, if you’re only going to be in Krakow for a few days and don’t have any prior interest in mining or sculpture, I’d recommend you stay in the city. There are plenty of amazing things to see in Krakow.

PS – When I visited, my tourguide instructed us not to lick the walls. When I told my relatives (native Poles) about this, they laughed at me and were shocked that I hadn’t licked the walls anyway. Apparently, it’s a tradition to disobey the guide and taste the salt wall. At the time, I thought it was a pretty gross tradition… but now I kind of wish I would have done it.