I was recently curious about wasabi, that spicy green paste you get with sushi in Japanese restaurants in case you didn't know, so I snooped around a bit a stumbled into this article on wasabi. I had no idea that real wasabi was extraordinarily rare and expensive and that the vast majority of restaurants use a mixture of horseradish and green dye in its place. I mean horseradish and wasabi are closely related, but it was a tad disappointing to find out that I've probably never had real wasabi.
Real wasabi, apparently, only grows under very rare circumstances, namely they need to grow with clean, flowing water with a particular mineral balance. There are only a handful of places that naturally have the right conditions, but people grow wasabi with hydroponics now. I think I should make it a quest to find some place where I can try real wasabi. =)