The Eyrie Building, as it is today, was completed in late 1994, when David Xanatos shipped Castle Wyvern from Wyvern Hill, Scotland and crowned the building with the restored castle. With the castle now above the clouds, the spell binding the survivors of the Wyvern clan was broken, and the sleeping gargoyles awoke. Mere hours after their awakening, the building was stormed by agents of an appearant rival corporation. During the battle, debris rained down on the busy streets below, garnering the attention of Elisa Maza. Her investigation led her to discover the Manhattan Clan living atop the building.
The building is a mini city in its own right complete with its own power plant, television production, kitchens, advanced scientific labratories, and self defense system installed by Owen Burnett and maintained by Xanatos's corporate holdings.
Such a defense system was capable of withstanding an attack from Oberon at full power. Owen installed the defense system as soon as he learned Fox was expecting, as it was thus likely that Oberon or Titania would try to take Fox's child. Part of the advanced systems were a powerful force field systemcapable of repelling even Oberon himself. It was eventually defeated from within when the building's internal generators were destroyed. It is unknown if it was ever reconstructed. The building, and buildings surrounding it also have, at various times, held facilities for launching steel clan and iron clan robot gargoyles, as well as anti-aircraft batteries.
In an alternate timeline set in 2034, The Eyrie Building formed the core of the Eyrie Pyramid, a dystopian fortress serving as the capitol of Xanatos's Soverign Nation of Manhattan. It was destroyed with the destruction of the cyborg Lexington in that timeline, though this timeline appears to have been entirely a construct of Puck.
When Xanatos moved Castle Wyvern from Wyvern Hill in Scotland to Manhattan he rebuilt it to pristine condition, repairing the ruin and decay the structure had endured while it was abandoned for a thousand years. More than that however, he modernized the Castle. ("Awakening")
The Great Hall, once the site of meals and entertainment for the royal court, was converted into a sort of main room or foyer. It seems all or most elevator access to the Castle from the rest of the Eyrie Building now comes there. The room is decorated with tapestries and for a time the Grimorum Arcanorum was stored there in a glass case. A main desk is present in this room and sometimes smaller desks, tables and/or chairs and other furniture is kept here. There exists a secret entrance to this room on the south wall.
A separate large dining room (with a working fireplace) was created elsewhere in the Castle. Presumably nearby was a large and very modern kitchen with walk-in freezers and enough space to prepare meals for many guests. In another area of the Castle is the "TV room". This small room has been used by the gargoyles for reading, watching television and relaxation. There is also a large library somewhere within the Castle. The library has two levels. A fully functional infirmary is present in the Castle. Fox probably gave birth to Alexander here and Goliath was taken here to be treated by Dr. Sato when he was wounded by Thailog on Halloween, 1996. ("The Gathering", "Bash")
The tower of the Castle once belonging to the Archmage and later the Magus has been converted into a laboratory. It was there that Coldstone was first awakened. ("Reawakening") Elsewhere in the Castle is a large room with many pillars. As there are no windows, it is assumed this is one of the lower levels. Xanatos set up the Cauldron of Life and imprisoned Hudson here. ("The Price")
Xanatos' and Owen Burnett's offices are located in the Castle as well. The gym and the control room used to operate the buildings defenses (see "Defenses" below) are probably located in the Castle as well. The front courtyard is often used as a helicopter landing site, though it is not the main helipad for the building (see "Helipad" below). It is unknown if the rookery or any part of it survived the move and reconstruction of the Castle, but it is possible.
Due to the many battles that have taken place here, sections of the Castle have had to be rebuilt several times, under Owen Burnett's supervision. ("Masque")
The Atrium is a large area located in the large space beneath Castle Wyvern. It is surrounded by glass windows and contains lush foliage and an artificial waterfall and stream with a bridge over it. Macbeth and Demona were enslaved here by the Weird Sisters and later the Coldtrio found their way into their new bodies here. ("City of Stone," Possession") The Atrium was also where Anastasia Renard, Halcyon Renard, Petros Xanatos, and Preston Vogel waited for news of Alexander's birth. In 1996, many New Yorkers attended Xanatos' Masque Halloween party in the Atrium. ("The Gathering," "Masque," "Bash")
On the North side of the building below the atrium is a large helicopter landing area. Though helicopters have often used the Castle Wyvern courtyard as a landing site, this area seems to be the dedicated helicopter storage and maintenance location.
The bulk of the building composing the lower two thirds of the Eyrie is office space. Many Xanatos Enterprises employees work here. Xanatos himself and Owen Burnett both have private offices of their own, however these are located far above inside Castle Wyvern.
Other places of note in the Eyrie Building include a huge generator room to power the vast energy needs of the building and a large gymnasium. The gym is probably located in Castle Wyvern, though given its size and the lack of evidence (stone walls, etc.) it could be elsewhere in the Eyrie.
The Lobby of the Eyrie Building is fairly standard. Many elevators lead here and there are also several massive starcases leading up into the building. At least one guard is on duty here.
In 1995, several additions were made to the Eyrie Building in the name of defense. First, powerful energy cannons were added to several of the turrets of Castle Wyvern. These cannons were mostly destroyed by Talon and the Trio in 1996, it is unclear if they were rebuilt or replaced by superior guns. Also that year, Owen Burnett authorized construction of a energy shielding system to prevent attacks and access to the building. This was mainly done to keep Oberon out, though Oberon eventually was able to bring down the shields by going under the building (the shield stopped at street level) and destroying the generators powering it. ("Kingdom", "The Gathering")