Coster Diamonds is one of the oldest diamond factories in the world and its professional craftsmen have been cutting and polishing expensive jewels since Moses Coster opened his first shop on Waterlooplein in 1840. Today you can take a free tour of the factory, which moved to its current location in three mansions in the Museum district in 1970. You can learn nearly everything about diamonds here in a variety of languages and discover helpful tips about how the four Cs (carat, colour, clarity and cut) influence the price of each gem. You can also watch men practicing their trade, learn how to spot fake diamonds and view replicas of famous gems such as the Koh-I-Noor which was re-cut by Coster at the request of Queen Victoria. After a brief tour you’ll be led upstairs to a diamond showroom where the owners hope you’ll be tempted to buy a diamond of your own. At the end of a labyrinth of more shops you’ll reach the Amsterdam Diamond Museum which charges admission, but you can also just exit the building if you’ve had enough sparkling carbon for one day.