The Fectra Building, not to be confused with the Fetra Building, it's similarly styled, but smaller counterpart located in Byzantium II, is a Byzantine governmental building located inside the OBGC Spectrum.
The Fectra Building was the first thing built on the inside of the Spectrum after the exterior was completed. (It was even built before the ship's anti-gravity unit was installed, which makes it the only building on the ship constructed in zero gravity.) The Fectra Building is 628 stories tall, making it the tallest building in Byzantine history, beating out the similarly styled, similarly named Fetra Building by 28 stories.
The Fectra Building is perhaps the most multipurpose building on the Spectrum, rivaled only by it's main sports stadium, the Spectrodome Multi-Functional Arena, which has a synonym for multipurpose in it's name. In addition to housing the Byzantine govornmental offices and command, it also houses the embassies to all the Central Powers squadrons, Ethon, Andron, and Adon. Also inside is a SkyClan base and a power plant, which houses three massive generators. The Fectra Building is so tall it actually touches the roof of the Spectrum's main living chamber with two massive beams that stick out of the top of the main building. This gives the Fectra Building another purpose as a support for the chamber. Those two pillars, which are about 200 feet long, are covered in mirrors to make their presence less noticeable.
The Fectra Building's design is based almost entirely on that of the Fetra Building back on Byzantium II, which is in turn based off the old Byzantine Capital Complex on Thyrm, which, in turn, is based off the stealth panels of the BFA Sigma, the seventh airship built by the Byzantine. So, it's based off an airship. However, the Fectra Building incorperates those two pillars, which actually run the length of the building.