The Citadel

Warning! Here there be spoilers.

The Citadel is a location in the Mass Effect series, as well as Every One That Asketh.

In Every One That Asketh, following the Reaper War, the Citadel was left hanging in Earth's orbit. In chapter 48, following a dream of Shepard's wherein she envisioned the Citadel and the Mass Relay were both back in place, it mysteriously returned to its old location in the Serpent Nebula. It remains the location for the Council.

Layout
In the Citadel there are several 'general' locations, which are known to those familiar with the Mass Effect franchise; the Presidium (the lovely park-like commercial district), the Citadel Tower where the Council convened pre-EOTA, the Wards (the five 'arms' of the Citadel where most residential and working areas are located), and the Spaceports, found on the inner central ring of the Citadel.

Zakera Ward
Zakera Ward is a hub location containing several shops, a club and a C-Sec office, along with Zakera Point.

Kithoi Ward
Kithoi Ward is home to the Council Central Archives, Taralos Amphitheater, Edroki Plaza, Larathos Institution, and Kithoi Point. It also has a Sensory Gallery where people can experience sensations the way other races do: smell like an elcor, hear like a drell, experience rain as a turian would, etc. It doesn't have a booth for thinking like an artificial intelligence, however.

Within the Kithoi ward, in the Tiberius Towers area, the Silversun Strip (home to Shepard and Garrus Vakarian's apartment) can be found... if one is very capable.

Tayseri Ward
Tayseri Ward boasts the Dilinaga Concert Hall, Museum of Galactic History, Auxua School of the Arts, Gaeron Botanical Gardens, and Tayseri Point. Dilinaga Concert Hall is the most damaged part of Tayseri Ward, and Tayseri Ward is the most damaged ward on the Citadel.

Bachjret Ward
Little is known about this Ward.

Shalta/Aroch Ward
In Mass Effect 3, two different names are given to this ward. Little else is known about it.

Galactic Standard Time
The inhabitants of Citadel Council Space utilize a standardized time system. This system is different from the Terran Universal Coordinated Calendar relied on by humans in that:


 * A galactic standard day comprises 20 hours.
 * Each hour comprises 100 minutes.
 * Each minute comprises 100 seconds.
 * Each second is half as long as a human second.

As a result, a twenty-hour galactic standard day is 15.7% longer than a standard twenty-four hour Terran Universal Coordinated day, which means it lasts 27 hours, 46 minutes, and 40 seconds in Earth-based time.

A galactic standard year is described as being an average of asari, salarian, and turian years and only 1.09 times longer than an Earth year. This means that a galactic standard year consists of 398.114 Earth days or 343.97 galactic standard days.

Defenses
While the defenses for the Citadel have taken a massive hit following the War, there is still a rudimentary Citadel Fleet protecting it; this is a selection of ships from nearly all races that patrol the area and keep out threats that would threaten the Citadel.

If any enemy gets close enough, the station is capable of closing in on itself to form a long, armored cylinder, 45 kilometers in length. The station's hull is sufficiently strong that, even when subjected to the most advanced weaponry available, it would take several days of sustained bombardment to inflict any serious damage to the superstructure.

Finally, there is internal security with C-Sec, and the Serpent Nebula itself helps to prevent trespassers from approaching in any unusual routes, due to the dangerous 'terrain' thereof.

The citadel also has turrets to ward off smaller ships, such as dropships.