The Citadel is the seat of power for the Galactic Concord. Resting in the sparsely populated Prome Cloud in the heart of the Concord, the Citadel is an ancient space station still filled with mystery and secrets left uncovered. It is the largest space station in Concord space, not including the Space Hulk, The Aegis of Time.
The Citadel was discovered by the Asari over 300 standard years ago. At the time, it was believed to be an ancient Prothean station. However, since the re-emergence of the Protheans it has been discovered that the Citadel pre-dates even the Protheans, and may be as old as the infamous Space Hulks. Attempts to date the strange compounds that make up the construction of the Citadel have proven fruitless as well.
The Citadel does have a "natural" inhabitant, the bio-mechanical Keepers. These strange creatures are a form of biological insectoid with extensive nanotech upgrades that are as much a part of them as lungs and hearts are to other species. The Keepers have never conversed with anyone, even now that the Citdael is home to millions of workers, security forces, ambassadors, and Senators. They go about their day keeping the Citadel up and running. They take no orders from anyone and ignore all attempts to communicate with them. If they are kept from completing a task, they will simply move on and return at a later time. Attempts to capture and study Keepers have largely failed as well. All Keepers that have been detained for study have gone into a kill sequence that not only destroys the Keeper, but breaks the corpse down into a gelatinous goo of base materials. Doubly frustrating is that all attempts to track the Keepers have failed as well. Their nanotech renders any attempt to track them with technology inert. Attempt to mark their shells wtih paint are also countered by their nanotech as the paint is broken down leaving their shells the original olive green in color. To date, it is unknown what the total number of Keepers on the Citadel actually is. Its also unknown if the Keepers mate or if they are clones, where they live on the Citadel, and if they are truly sentient or some form of bio-mechanical drone controlled by a central computer or even by an unseen being living in the Citadel. What is known is that they are an integral part of Citadel maintenance, and are protected by law from the current inhabitants of the station. Interfering with a Keeper in its duties and causing harm to a Keeper is met with hefty fines and even the threat of incarceration and or banishment from the Citadel.
The Citadel was not originally home of the Concord. When the Great Alliance first formed, the Sol Systems Alliance space station, Babylon 8, was chosen as a headquarters. However, once the Illithid Invasion was broken and the Galactic Concord was established, it quickly became obvious that the aging space station was going to prove insufficient for the duties of the Concord. The Asari offered the Citadel as an option grudgingly at first. The Asari had kept the discovery of the Citadel a secret for many years. Even when word about the Citadel leaked, they kept the station under strict guard, only allowing rigorously vetted science teams access to the facility. As the Galactic Concord grew, and the possibility of any planetary body being a home quickly ruled out, the Asari offered the Citadel to the Concord on the condition that they be granted a permanent seat on the Council.
The Citadel consists of six areas, five wards (Zakera, Kithoi, Tayseri, Bachjret, and Shalta), each spanning an arm of the station and are metropolises in and of themselves, and the Presidium, which houses the Senate. The Wards are each vast cities, complete with neighborhoods, shops, entertainment, and infrastructure (shipping/recieving, waste removal, etc.). The Keepers maintain the overall integrity of the Citadel, but the Concord employs workers to maintain the systems that have been installed to ensure the survival and comfort of Concord member species and visiting delegates from other stellar nations. Each Ward has a population of roughly 8 million people. An artificial atmosphere is maintained at all by the highest floors of the various skyscrapers that dot the Wards, so the streets and thoroughfares are essentially open to the void of space though kept a comfortable temperature and gravitational force for most species. Specialized atmospheres and accomodations for species that do not breathe oxygen or have other environmental requirements are provided in certain areas of each Ward.
Each Ward has its own feel, but there are some constants. Generally, the ringward sides and the edges of the arms hold the most expensive and posh neighborhoods in each Ward. Zakera is widely regarded as the safest Ward. Bachjret is generally regarded as the poorest Ward. However, each Ward has their good and seedy areas. Generally, the deeper into the Ward that you go, both long-ways and under the surface, the seedy the areas get. As it goes in most cities, the further from the light a society gets, the more the criminal element moves in.
The Presidium is the central ring of the station. Most of the buildings here are related to Galactic Concord business. The Senate is housed here in the Spire, the large tower that stretches from the Presidium ring to the center of the Citadel ring. The offices of many of the senators and Concord agencies are also housed in the Presidium, as well as the homes of the Council members. As the Galactic Concord continues to grow, many agency offices and some senatorial offices have moved to the ringward portions of the Wards. The Presidium is enclosed, complete with a holographic sky (set to the Concord standard 20 hour day). The Presidium is also home to the most beautiful park space and highest end shops and restaurants in the Citadel.
Security is tight on the Citadel. C-Sec controls the flow of people coming and going at the customs offices located in several points in each Ward as well as being the everyday police force. As would be expected, the threat of terrorism on the Citadel is high, so keeping close tabs on who and what are coming aboard is a constant concern. The Concord Navy also maintains a presence in and around the Citadel. The Bastion, the headquarters of the Concord Navy, is housed on the far edge of Kithoi Ward. There are also five dreadnaughts, two carriers with full fighter squadrons, and a full battalion of troops are stationed on the Citadel as well. Add in the orbital defenses, the cannon batteries installed by both the Asari and the Concord, and the ability for the Citadel close the Wards in together for maximum protection and the Citadel is one of the most heavily defended installations in the galaxy.
Despite the security, there is a thriving criminal element on the Citadel. The marging of various cultures and societies leads to a veritable smorgasbord of vices and appetites to sake. Various gangs, syndicates, and cartels all maintain a presence on the Citadel. Smuggling in contraband is a full-time job for these organizations. Despite the best efforts of C-Sec, contraband makes it through both by the ingenuity of the smugglers and the bribes given to C-Sec customs officials.