Citadel

The Citadel is an ancient deep-space station, constructed by the Leviathans. Since it's transformation into the core of the Reaper's extinction cycle, countless species have come to call the Citadel home, and most used it as the political, cultural, and financial capital of their governments. In today's galactic community, most species maintain embassies on the Presidium, the Citadel's inner ring, to represent their interests.

The Citadel Tower, in the center of the Presidium, holds the master control unit and the Citadel Council chambers. Council affairs often have far-reaching effects on the rest of the councillian galactic community. Five arms, known as the wards, extend from the Presidium. Their inner surfaces have been built into cities, populated by millions of inhabitants from across the galaxy.

The Citadel is virtually indestructible. If attacked, the station can close its arms to form a solid, impregnable shell. For as long as the station has existed, an enigmatic race called the keepers has maintained it, allowing it's users to live on it without gaining access to it's "dirtier" functions. Gravity is simulated through rotation, and is a comfortable 1.02 standard G's on the Wards and a light 0.3 standard G's on the Presidium Ring.

Specifications
Although the Citadel is equipped with mass-effect-generating element zero cores, most of the gravity on the station is generated by the centrifugal force of rotation.


 * Rotation: 3.5 minutes per revolution
 * Rotational Gravity in Wards: 1.02 Earth
 * Rotational Gravity in Presidium: 0.3 Earth
 * Total Length (Open): 44.7 km
 * Diameter (Open): 12.8km
 * Ward Length: 43.6km
 * Ward Width: 1.44km
 * Presidium Ring Diameter: 7.2 km
 * Presidium Ring Width: 553 m
 * Exterior Armor Thickness: 330 m
 * Population: 13.2 million (not including keepers)
 * Gross Mass: 7.11 billion metric tons
 * Height of the Presidium Tower: 1047 m

Modern Discovery
The asari were the first modern race to discover the Citadel, soon after learning to use the mass relays. They were joined shortly by the salarians, and soon after, the volus. As other races were contacted by the asari, or discovered the station independently, they gained embassies on the Citadel and came under the jurisdiction of the growing Council, eventually comprised of the asari, the salarians, and the turians.

Strategically located at the junction of a number of mass relays leading to various parts of the galaxy, the Citadel quickly became a hub of activity. The station was chosen to house the Citadel Council, thereby cementing its importance in the galactic community. It is accepted to be the political and cultural heart of Citadel space, the unofficial name given to all systems that fall under the Citadel species' control.

Legacy
The Citadel was not, in fact, constructed by the Protheans; they were simply the last race to make use of the station before the asari arrived. It, and the mass relays, are the creations of the Reapers, and were built to help facilitate their cycle of galactic genocide. The Reapers were also responsible for the placement of the keepers on the station, in order that the occupying races would not discover the Citadel's key functions. The station is actually an inactive mass relay leading to dark space, designed as an elaborate trap so the Reapers can wipe out the heart of galactic civilization and leadership in a single, devastating strike.

According to Vigil, the last Protheans used the Conduit and traveled to the Citadel to try and break this cycle. They succeeded, but it was already too late for the Protheans. Because the Conduit portal only linked in one direction, Vigil feared that the Prothean scientists, unable to find any food or water on the Citadel, slowly starved to death. Due to this Prothean intervention, the Reapers were forced to travel to the Milky Way without the help of the mass relays, at normal FTL speeds.

The shibboleth includes a warning that the station is a dormant trap.

Layout
The Citadel is a massive construct, similar in shape to a pentagram. It consists of a central ring 7.2 kilometers in diameter, from which five arms protrude, each 43.6 km long and 330m thick. The station is capable of closing in on itself, via the convergence of its five arms, transforming it into a 45 km long, impenetrable cylinder. However, the Citadel is only closed in times of emergency, and normally the station retains its 'open' appearance.

The central ring and five arms are home to the Presidium and Wards respectively; the spaceports are also located on the central ring, as it is the center of rotation, facilitating easier access for ships attempting to dock with the station.

The Citadel has a labyrinthine interior superstructure, accessible through keeper tunnels.

Wards
The majority of the Citadel's population lives in the Wards, the five massive arms of the station that house the residential and commercial districts. Many galactic races have established cultural enclaves here. Population density and cost of living are extremely high, akin to Earth cities such as Xiānggǎng and Singapore.

Clockwise, the wards are named Zakera, Kithoi, Tayseri, Bachjret and Aroch.

The Wards are divided to four layers. The lowest level houses the labyrinthine interior. Above this level, the Citadel Archives function as a repository for artifacts and records deemed important. The labyrinths can be observed from the archives. Above the archives, the atmosphere container, in average about 70 meters tall, is located. The vacuum-exposed upper layer, starting from the Ward Roof, is open-topped, with hermetically sealed skyscrapers rising from the superstructure.

The view from the Wards is spectacular. In the background, stars, Serpent Nebula, and the nearby blue giant called "the Widow" move across the sky as the station rotates to stabilize itself. In the foreground, the lights of buildings and vehicles on the opposing Ward arms perpetually shine. The Citadel has no real day or night. While the station keeps to standard galactic time for political functions, business rarely close, and residents acclimate to sleep and work according to personal need rather than a day-night cycle.

Additions and modifications are constantly being constructed, though they must stay within certain specifications that will not compromise the operation of the station. Occasionally, the keepers will descend on an area of the Wards and move or change the architecture, likely to ease a potetial repaer invasion. Residents have learned to live with these inexplicable intrusions.