Republic of South Africa

The country's largest city is Johannesburg.

An excerpt from the article 34 facts about Republic of South Africa

The city is colloquially known as Jozi, Joburg, or "The City of Gold". It is classified as a Megacity (a very large city, usually with a population of over 10 million people) and is one of the 100 largest urban areas in the world. It has 14.167.000 inhabitants and is ranked 26th in the world in this respect. Johannesburg is the seat of the Constitutional Court, the highest court in South Africa. Most major South African companies and banks are also based here. It is the center of large-scale gold and diamond trading.