Johannesburg, informally known as Jozi, Joburg or "the city of gold", is the largest city in South Africa and one of the 50 largest urban areas in the world. It is the provincial capital and largest city of Gauteng, which is the wealthiest province in South Africa. Johannesburg is the seat of the Constitutional Court. The city is located in the mineral-rich Witwatersrand range of hills and is the centre of large-scale gold and diamond trade. It was one of the host cities of the official tournament of the 2010 FIFA World Cup.