Explore the Gassan Diamond Factory in Amsterdam. it's home to the only original Gassan 121 diamond. This diamond has 121 facets, 16 additional facets on the top and 40 extra on the bottom. Take a tour or just explore it by yourself. Do you want to take a tour? It's FREE! There's multilingual guides, tours 7 days a week, all year round. Open 9am to 5pm. The tour lasts about an hour. You can see them cutting diamonds right before your eyes! Complementary beverages are included along with parking for tour buses. Take the canal tour boat to the factory. Or simply find it on Nieuwe Uilenburgerstraat 173-175 in Amsterdam. The location is right on the water. Buy a ring, see diamonds being cut, or just enjoy the atmosphere.