Terra is the human homeworld. The entire planet is made up of one large city, with multiple layers. The deeper you go, the more dangerous and unsavory the world appears, with poverty starting in the second and third levels, and darker things appearing even lower. Terra has two moons, both of them terraformed to support life.
The Layers of Terra
Topworld: The uppermost layer of Terra, also the nicest. This includes the location for the upper and middle classes of the world, as well as the home of the government, and Human council.
The Hub is the largest place here for players, and is a giant player-run shopping district, as well as where the NPC and Player request listings are posted.
Eden is a good place for players as well, consisting of a park, the archives, the storage vaults and bank. Also here is the Games Center, a place to unwind and place some money on the line for fun, and the Parliament buildings.
Sector 00: The main military and police home base on Terra, this is where to sign up, and where players involved in the military go for rank-ups and to launch the higher-up missions. The lower ranks they can get at Areas 01-09, other headquarters around Terra.
The Starport: This is where players dock their own ships, as well as catch the shuttle to other planets in the system. A shuttle will not go to a planet if Humans are at war with the race it belongs to, so you might have to catch a ride with other players. Some will make you work, some will make you pay for the trip.
Second World: Not too bad of a place, if you take a look at the layers below. This is where the "Bad" parts of town, that are still livable are. The Lower class live here, as well as most of the clubs and entertainment around Terra.
The Arena: This is where players and some NPCs fight to the death, only to be revived by the staff. A good way to make money, albeit dangerous.
The Lower City: This is where you would go if you wanted to see the lower side of things. Gangs, many homeless, and the poorer of the lower class live here. The place is a mess, and with no help from the authorities, it doesn't look like it'll be cleaned up anytime soon.
The Pits: The fourth and final layer of Terra, this is a complete wasteland which could probably be considered the most natural the world gets. Many dangerous things live down here, as well as debris from above and the ruins of the ancient cities before the world was turned into the futuristic one it is now.
Old Terra Ruins: What used to be the largest city on the planet long, long ago is now sinking into the world itself. This place is filled with dangers from hostile machines to ancient creatures alike. Probably better than what else the Pits have to offer.
Terra's Moons
Torus: The larger moon of Terra, this is an Earthlike moon, with a temperate climate. It has a few cities, but nothing compared to Terra itself.
Shi: This is a backwater moon, with more untamed wilds than settlements. It has two major cities, and some minor outlying towns, but mostly it's home to some of the more noteworthy creatures, such as Pegasus, Centaur, and some Dragons.