Diamonds are traded at a diamond bourse, between the bourse members. The goal is to promote the interests of the local diamond industry. In addition, the diamonds, whether rough or polished, do not necessarily have to be physically present at the diamond bourse. More importantly, those present must be able to negotiate. The diamond bourses are always very well protected and only accessible to members. They can be found in, among other places, Antwerp and Amsterdam. Antwerp is the only city in the world that has four diamond bourses.