Amsterdam has a long heritage of diamond trade and industry – the city has been a major diamond centre since Sephardic Jews introduced the diamond cutting industry in the later 16th century. Nowadays there are about a dozen diamond factories in the city, several of them offering guided tours. The tours are free and are usually conducted 9am to 5pm every day. Diamonds aren't necessarily cheaper in Amsterdam, but prices are fairly competitive. Additionally you will an opportunity to see how they cut and polished, and you will receive an extensive description of the purchase so you will be able to know exactly what you are buying.