Mponeng is an ultra-deep tabular gold mine in South Africa in the Witwatersrand Basin of the Gauteng Province.[1] Previously known as Western Deep Levels No1 Shaft, the mine began operations in 1986.[2] It is one of the most substantial gold mines in the world in terms of production and magnitude, reaching over 4 kilometres (2.5 mi) below the surface.[3][4] At this depth Mponeng takes the title of world's deepest mine from ground level, with aims to deepen the mine beyond 4km in order to reach more reserves.[5][6] A trip from the surface to its deepest point takes over an hour. An Ecuadorian marathon runner completed a half marathon within the mine in 2017.[3][7] The mine supports a very large number of people, companies and industries, including entire towns and cities.[8]