The city center, developed around a small historic center, represents less than a quarter of the total area of the city, which has spread along the valley and has also been connected in recent years with satellite cities in the states of Miranda and La Guaira, creating a major metropolitan area known as Gran Caracas. The city's rapid population growth has resulted in increasing traffic congestion. To this end, the subway transportation system (Metro de Caracas) has been progressively expanded and is currently linked to the Los Teques Metro and, in the future, to the Guarenas-Guatire Metro system. The "Ezequiel Zamora" Central Railway System also links the communities of Charallave and Cúa de los Valles del Tuy with the subway transportation of the capital city.