Hokitika Sock World 

Finding a yarn store here is surprising enough, but the store has a focus on sock yarn. Not only that but it also houses a sock machine museum and makes new sock-making machines if you want to own one. To my mind the model of sock they make isn't quite what I like (the heel is a bit of a bodge and the price of $3750 is a bit off-putting) - but that said, if I'm to get through my stash of sock yarn before I die, I might have to resort to using one. 

(It's also a general yarn store - so theres plenty of interest for every knitter or crocheter, making Hokitika well worth a visit just for this store.)