Cullinan Diamond Mine is located about 30 km east of Pretoria in the small diamond mining town of Cullinan. It is most famous for producing the largest diamond ever found: the "Cullinan Diamond," unearthed in 1905, weighing in at 3,108 carats. The largest diamond cut from the Cullinan Diamond was named the First Star of Africa and is now mounted on the Sceptre of the Cross, one of the British Crown Jewels. The mine was sold by DeBeers to Petra Diamonds in 2007, and since has continued to produce huge exploits. In 2008 a 480 carat diamond was found that sold for US$18 million, and in 2009 a 507 carat diamond was found and is expected to catch above US$20 million. Tours are available of both the above ground (1.5 hrs, R60) and below ground operations (must arrange in advance, 4hrs, R440), where you can check out the working mine operation and diamond cutting and polishing.
To get there from Pretoria, take the N4 East to the R515 exit, then turn left and follow the signs to the diamond mine.