Though no longer the diamond capital of the world, Amsterdam is still one of the major centers for diamond cutting. The largest diamond ever discovered, the Cullinan (from which the Star of Africa was cleaved), was cut in Amsterdam. Even if your budget doesn't stretch to buying a gem, it's worth visiting one of the diamond factories near Dam Square for a free tour to see cutters and polishers at work.
Diamonds
Historic diamond-cutting center with factory tours and showrooms