Everyone knows city office towers have basements. There must be somewhere to house the custodial staff, the mechanical systems, and the storage of items such as unused furniture, paper towels, and holiday decorations.

Basement Level 1 under the massive Corona Tower spills out to cover the entire Corona Tower mall, stretching eight blocks in every direction. That's 64 city blocks of basement on just this one floor.

Basement Level 1 is enormous, offering room for just about anything the builders of the Tower could envision. The first priority? Parking. A structure such as this needs a lot of staff to keep it operational, and that much staff needs a lot of parking. Fully one third of Basement Level 1 is reserved for parking for the five-level basement research complex. Also, visitors (only invited of course, and few of those) will find staffing offices, business offices, three conference rooms, military housing for long-term residency situations, two commercial kitchens, a dining hall, and a foyer/public space/lobby with ample space to meet-and-greet.

The first thing you will notice upon entering Basement Level 1 is the ceiling height. It soars to twenty feet, with much of the space open and airy. Bright colors, sleek furniture, and modern art lend a museum-like quality to the space. 

At least in the foyer/lobby. This is a place that doesn't feel the least like a basement. Come on in. Enjoy the coffee. The weather's fine all the time.

Although we don't visit until in a later book, we learn of Basement Level 1 in Book 1 of The Human-Hybrid Project, Shattered by Glass.

Basement Level 3 has less space than Basement 1 or 2. Each basement is reduced in size in comparison to the one above it.

When Garik first visits Basement 3, it has a "squashed" feel to him, as though the Tower is pressing down on it and compressing the walls. The ceilings are lower, the hallways narrower, the living quarters smaller. Even the finishes on the walls are of less quality than on the two floors above.

Basement 3 contains living space for the failed hybrids, many of which are perfectly functional but not able to mingle among normal people without attracting attention. Basement 3 has separate kitchen and dining facilities for its occupants.

On this level are also the soundproof training facilities. These facilities comprise the bulk of the space on Basement Level 3.

We first visit Basement Level 3 in Book 2 of The Human-Hybrid Project, Inside the Darkness.

Garik Shayk wakes up in his new quarters on Basement Level 2 at the beginning of Book 2, Inside the Darkness.

As we move down each level in the basement system, they get progressively smaller, although that's only relative to the enormous 64-square-block Level 1. Basement 2 loses some space that is given over to parking in Basement 1, but to walk the corridors and learn the various sections on this level is still a prodigious act of will.

One entire section of Basement 2 is allocated to the research facility's labs, which are extensive. Also, since many of the researchers are not from Bay City, a generous portion of Basement 2 is allocated to housing, including a two parks, an "outdoor" pool, and dwarf trees lining street-wide corridors, all known as Corona City. It's all done to minimize claustrophobia and burnout. The Corona Corporation quickly realized it's easier to retain people than it is to retrain them.

Also on Basement 2 are quarters for the successful hybrids, a large recreation center with specialized activity areas for various strains of hybridized humans, an emergency clinic (the actual hospital is two floors down), and a combined snack and break area with a small, fully stocked kitchen. Everyone on Basement Level 2 is requested to dine in the cafeteria on Basement 1, unless their quarters has a full kitchen and they are fully prepared to cook and clean up after themselves.

The recreation area on this level includes a two-story climbing wall that juts into Level 1, with windows for the military crew housed there to observe the climbers good enough to display their skills on the most difficult routes; a full glass-walled water room for those who are aquatic-adapted; boxing facilities; running tracks; and other sports venues.

We are introduced to Basement Level 2 in Book 2 of The Human-Hybrid Project, inside the Darkness.

As we descend each level of basements in the secretive Corona Tower human-hybrid research facility, the total floor space shrinks, often due to underground untilities that couldn't be easily rerouted, and at other times to allow for what is located on the floor just above. Level 3 contains the natatorium with its deep-water pool, meaning Level 4 is notched out to provide room for the pool. The same is true for each of the basements, levels 2-5.

Basement Level 4 contains the facility's hospital, a cafeteria, and storage areas equaling several city blocks. Medical personel can access the underground parking garage on Level 1 with direct access through the hospital's dedicated elevators located just north of the cafeteria. Access is by passkey only, and only for hospital staff.

Access for pool maintence on the floor above and the storage tanks that extend through the bottom four levels of the basement complex are also part of Level 4's duties. 

During quiet hours, the rumbling of the power plant on the level below creates a low-key background hum in the hospital rooms, and the right-of-way for the city's underground utilities sometimes gurgles and spits with watery noises.

A distinctive feature that makes the hospital level stand out is the blue striping on the edges of the floors, giving the corridors the look of ribbon candy. The air is clean, with no odor of its own, providing a distinctive aroma unique even in the research center. The reason? The air is scrubbed, purified, and kept separate from the air pumping in and out of the other basement levels. No diseases in. No diseases out. What every good hospital should strive for.

Garik Shayk awakes in the hospital on Basement Level 4 at the end of Book 1 in The Human-Hybrid Project, Shattered by Glass.