Babylon'The Gleaming Jewel' in Outremer's crown, Babylon is a true engineering marvel. One thousand miles across with skyscrapers bursting into the cloud cover, it is home to over four billion men, women and aliens. It's the cultural, military and economic powerhouse of the system and a major contender for most influential city in the cluster. Crammed full of bright neon lights, debauched clubs, ancient banking societies and experimental weapons manufacturers, Babylon is home to a very diverse population with differing beliefs and ideologies. It's a mystery in itself as to why 90% of the population gathered in one spot on a planet so large and diverse; most put it down to the 'colony sheep' effect. Another theory is the comforting atmosphere provided by the twelve Alien Towers arrayed around Babylon. Originally they protected a Rahtu city until at the end of the First Contact War Humanity built Babylon over it. They all shoot some unidentifiable energy into the air and all the beams link up directly above the middle of the city. This in turn creates a Biosphere which is hardly visible to the human eye. It keeps the temperature down, creates artificial rain which waters the city park's manicured gardens, shelters them from the blistering sandstorms and generally makes the inhabitants feel as if they aren't really in a gigantic desert at all.
Walking into Babylon itself, you will soon find out there are hundreds of districts that are often jumbled together and jostling for attention. Buildings of all different sizes and shapes sprawl out for as far as the eye can see. Huge skyscraper-like blocks of apartments that link together via huge walkway have long been considered the only rational way for residencies to be built here. This maximizes space efficiency seeing as there is a sore lack of it within the Biosphere. Of course this isn't always the case, the buildings get smaller and more individualistic the closer you get to the Biosphere Rim, with houses getting more ornate.surrounded by plush gardens. There is These properties are owned by the business owners and corporate elite.The consensus within Babylon is that the closer to the Skytower you live, the lower your class and status.
The rich on the outskirts do have to deal with the daily threat of bandits and other unsavories breaching the Biosphere defences, but in recent times the construction of a ring-wall that circles the entire city, complete with a standing army and auto-turrets, has decreased the risk of a full scale invasion or infestation by Maw Worms or Sand Pirates. The forces at the wall have a much tighter grip on all the traffic that comes into Babylon from the Desert; they can sort the legitimate traders from the 'scum and terrorists'. Airships flying into the Biosphere must identify themselves or risk being pursued and shot down by BESC.
Of course, there is a quota of land within the Capitol that has been set aside for nature reserves and other features. Interlocking nature with the sleek beauty of the architecture, parks, monuments and lakes dot the Capitol, wildlife encouraged to embellish the authenticity. But the center of the Capitol is where most of the action is. Located on an island surrounded by man-made moat; skyscrapers and public buildings fill the horizon, each vying to be the highest and most prestigious. This epicenter is where the majority of the banks, bureaucratic agencies, corporate headquarters, the infamous Skytower and of course the BESC nerve center are kept. The Babylonian Council is also located at the epicenter. That is where the various ministers meet to discuss matters of importance.
Moving through the legendary Biosphere that hangs above the Capitol, the heat hits you like a wall and the sun suddenly seems a lot brighter. You are confronted with a barren desert as far as the eye can see. Dunes of rippled sand, with streams of fine dust blowing gently atop it, creating a mirage of elegance, like a painting against the bleak barren landscape. The tall brown peaks way off in the distance show the edge of the Desert, stretching up to grasp at the clouds far above the searing sand and casting a stretched, dark shadow across the wasteland. The mountains and desert are, for the most part, completely barren. There is little to support life outside of the Capitol, aside from the odd oasis; which are few and many miles between. Such oasis's are often small, surrounded by patches of grass with a few trees and bushes. However, in a dry, arid landscape such as the desert, even the smallest patch of grass and shallowest watering hole is akin to a gift sent from the stars.
The Babylon State includes the desert surrounding it, however BESC have nigh on given up trying to control the badlands which feature a myriad of hideouts and anchorages. Shantytowns have sprung up in the shadow of all twelve of the Alien Towers which are all equidistant from Babylon. These shantytowns are a hive of criminal activity; Chop shops, black market souks, blood sports, counterfeit weaponry and ammo as well as slavery (human, alien and Machine.) They also harbor the thriving industry of manufacturing and selling of Sandships as well as refurbishing old or stolen ones. This is a practice BESC has outlawed and furthermore is trying to stamp out, however they often don't dare venture into the towns except to maintain or study the Towers. The resistance they encounter from the locals is often fierce and violent. However there have always been assumptions that BESC spies, informants and agents keep tabs on powerful individuals and are implicated in the regular assassinations that occur.
Edessa
A city of fifty million situated around ten thousand miles Northwest of Babylon, Edessa supplies the whole of Outremer with clean and fresh water. It's not the only source of H2o but if transport of its water ceased, Babylon's population would be in deep trouble. Six high speed, non-stop, underground Mag-Railway lines run huge tankers of water to and from the capital at close to an eye watering ten thousand miles an hour. They reach the Biosphere in 67 minutes, unload their cargo into gigantic reservoirs and head off to get the next batch. In addition to that, pipes and waterways are slowly being constructed to flow directly in Babylon. Constant raids by pirates and bandits from the desert sands has slowed construction considerably, which is why Babylon relies so much on the trains. Nonetheless, they are nearly finished, some of the pipelines being barely five hundred miles away from the Biosphere. Edessa is situated on the rim of a colossal crater, connected to a series of underwater lakes. Rivers from all over flow into this crater, which then leads into the sea. A multitude of dams control the flow of water every step of the way and generate electricity for the entire city.
Actim
A city of seventy five million full time inhabitants situated about ten thousand miles Northeast of Babylon, Actim is one of the most renowned tourist centers in the Cluster. Citizens sick of their life, high ranking Babylonian officials and the rich and influential from planets millions of miles away from Outremer flock to this city in their millions to enjoy cool sea breezes, gorgeous beaches and 'the most exciting cocktails in the galaxy!' The variety of activities and range of establishments is baffling, one can play Vrangan Prang on the beach with buddies in the morning, be lunching on lobster in one of the privately hired glass submarines that explore the beautiful coral reefs in the afternoon and be hobnobbing with most glamorous people on the planet in the skybar 'Ciel de Paris' by nightfall. Restaurants serving delicacies to suit absolutely every taste are on every street corner. Shops were you can buy luxuries from the galaxy over sit illuminated by sumptuous white lights on every boulevard.
Réunion
A city of twenty million situated almost ten thousand miles South of Babylon, Réunion is the capital's main supplier of food, fruit and vegetable matter. Animals, plants and trees of every conceivable variety are force grown in perfect conditions inside thousands of circular green houses and farms, to be shipped off to Babylon on six high speed, non-stop, underground Mag-Railway lines, much like the water that comes from Edessa. The population of Réunion are almost all involved in the food trade, helping to maintain existing greenhouses or build new ones. They all choose to live in thin towers that double as research facilities. Here corporations invest time and money into advanced Genetic Modification techniques, for food as well as sentient creatures. From above Réunion looks like a neural network, with a vast complex of greenhouses being linked by walkways and accommodation towers.
The Desert
Blisteringly hot, arid and very very dangerous. The desert sands are no the only danger to anyone stupid enough to venture out into the Badlands on their own. The Desert is roamed by Sandships full of Pirates, raiding innocent barges and land vehicles for their stuff. There is also the issue of dangerous fauna to contend with. Maw Worms, Pclendathun and other rarer beasts are all carnivorous and will most likely attack upon sensing your presence. Go in a convoy! Or even better, fly out of there all together. Keeping Babylon's immediate atmosphere at a nice level are twenty four large Alien Towers which circle the city at equal distances. Over time, settlements have sprung up around each of them. These Tower Towns range in size from twenty thousand to two million, though a lot of the inhabitants are only in residence for short periods at a time. These towns are dirty, ramshackle and quite often a hive for criminal activity; most buildings are made from rudimentary construction materials such as brick and sheet metal and gang graffiti and propaganda is everywhere. Humanity in the desert is not limited to these Tower Towns though.
To give you a flavor of whats out there, you can see here decrepit little havens built out of a graveyard of Sand Ships.

Little Souks thriving beneath the wheels of abandoned super transports (Krupp Corp gear mostly)

There are also vast wind farms, protected by brutal and highly paid packs of mercenaries.