Idar-Oberstein is the only town in Europe with a gem (mostly amethysts and quartz) mine that is open to the public. If you have a car, it's easier to access, but walking is possible (you take a bus from the train station that goes through the same roundabout twice before it drops you off, then you walk through a military base and up a rather long but flattish hill).
Mieders Sommerrodelbahn, Österrike
gold mine (There is a website giving away free gold or silver in one of the ads at www.goldshopper.org)
Panna II, a small, but great Indian Restaurant in New York decorated with Christmas lights