Johannesburg is one of the most important economic, political and social centres in Africa. The city's history dates back to the 1880s when the shanty outpost town was transformed overnight by the discovery of the largest gold deposits in the world. Johannesburg is the largest city in the world not built on or near a major water source, and this is testament to the magnetic draw of the millions of immigrants that have since come to this city of gold. The Central Business District of Johannesburg has, unfortunately, undergone a depression in recent years, resulting in many businesses moving north to the nearby area of Sandton. However, the revival program currently in place promises to rejuvenate the CBD into one of the most colourful and cosmopolitan cities in the world. Due to the CBD's depression, new projects in central Johannesburg have been sorely lacking. The majority of the skyscrapers in central Johannesburg date from the boom of the 70s and 80s when the city took on a mini Manhattan feel, and the only major new high rise projects that have been implemented in Johannesburg are those in the surrounding areas, such as Sandton, Midrand and Bedfordview. Despite this depression, Johannesburg is the mecca for shoppers, and is a popular shopping destination for many Africans from other sub-Saharan countries, who come shop at some of the biggest shopping malls in the Southern Hemisphere. The city's nightlife is alive and well, and Johannesburg International Airport is the biggest and busiest in Africa, meaning that 'Joburg' or 'Jozi' (two other affectionate names for the city) is the transport hub of Africa. The city is also a major centre for education and research, with two large universities catering not only to South Africans, but many other students from other African countries and abroad. Johannesburg is also one of the least expensive cities in the world and has only recently been overtaken by Ascuncion, Paraguay as the cheapest city in the world to live in. It has been said that Cape Town has beauty and serenity to relate to; Durban has a warm ocean to relate to; the only thing Joburg can relate to are its people, and therefore it is the people that are the city, and the reason why the city will never stop beating with new opportunities and the potential for growth, which hasn't even neared the breaking point.