Lagos is a city in the Nigerian state of Lagos. The city, with its adjoining conurbation, is the most populous in Nigeria, and the most populous on the African continent. It is one of the fastest growing cities in the world, and also one of the most populous urban agglomerations. Lagos is a major financial centre in Africa; the megacity has the highest GDP, and also houses one of the largest and busiest ports on the continent.
Lagos initially emerged as a port city that originated on a collection of islands, which are contained in the present day Local Government Areas of Lagos Island, Eti-Osa, Amuwo-Odofin and Apapa; the islands are separated by creeks, fringing the southwest mouth of Lagos Lagoon, while protected from the Atlantic Ocean by barrier islands and long sand spits such as Bar Beach, which stretch up to 100 km east and west of the mouth. Due to rapid urbanization, the city expanded to the west of the lagoon to include areas in the present day Lagos Mainland, Ajeromi-Ifelodun and Surulere. This led to the classification of Lagos into two main areas - the Island, which was the initial city of Lagos, before it expanded into the area known as the Mainland.