Midgar
A world of industry and corruption. Midgar was once a vast city on the planet Gaia, controlled by the powerful ShinRa company. The city is made up of 8 sectors surrounding the skyscraper known as ShinRa HQ. Each area is connected by various trains. When the heartless attacked and took part of the heart of Gaia, a piece was located directly in the middle of the vast city. That piece saved the city as it floated their space, reforming the ground below it to make it a planet in and of itself. The heart guided the planet into space of other planets facing the heartless as well.