School District 22

School District 22 (第二二学区) is the smallest school district in terms of surface area in Academy City, with most of it being located deep underground. Only 2 km2, School District 22 is mainly used for developing technology for an underground complex in the faces of land shortages in major cities.

Principles
Occupying only 2 square kilometers, it is the smallest district of all Academy City. However, it is developed underground about several hundred meters in depth, and is referred to as the district with the most scientific style.

According to Kamijou Touma, underground complexes like School District 22 aren't suited for Japan, due to earthquakes. However, according to Itsuwa, the district is actually safe against earthquakes, and claims that the reason the district spirals underground is because it acts like a huge spring, which can absorb the impact when there's an earthquake, though Touma states that it is simply a baseless rumor.

Above ground
On the surface there are no buildings, as wind turbines cover the district. However, most of the turbines on the surface are different from the rest that appear in Academy City, piled up or arranged on top of one another in a manner which resembles a 30 story tall jungle gym. The reason is that the underground complexes that extend downwards require a lot of electrical energy, and the district cannot rely on regular wind-generated electricity or solar-generated electricity.

Most of the energy is used to pump air in, absorbing oxygen from the surface and removing the carbon dioxide accumulated below. There is also a need to pump rainwater and wastewater up. With all these in consideration, 40% of the electricity consumed in Academy City is put into use for the large air pumps.

Below ground
Underground, the district is a giant cylindrical area, continuing to extend down to the bottom in a spiral. The district is separated into 10 underground levels (階層). The path into the underground complex has two lanes, one to go up and the other to go down, probably for vehicles. However, there are also apparently pedestrian entrances like a spiral stairwell to another level. The hardness of the district's floors is equivalent to that of safety shelters.

The ceilings on all of the underground complexes, in contrast to the orange lights in the tunnel that leads into the underground complex, the level has ceiling that has become a planetarium projection panel, made out of bulletproof fiber screen, passing through a camera to form a an artificial night sky. The roof of the underground complexes is like a ceiling of a sports hall, supported by a large amount of metal frames that scatter the weight. However, since the architecture alone doesn't seem able to support its own weight, there are apparently other ways used to support it, though they are currently unknown.

Since it acts like a projection screen, it can display typical announcements and news like the ones on the airships if needs be. Each level is probably equipped with buildings that can provide oxygen to people when there is a "no oxygen alert" in the level, and seal the entrances as so not to allow air to enter the building.

Each level of the underground complex uses an artificial river that flows into a waterfall to generate power.

Third Level
The third level bears several buildings and establishments. It also has artificial forests and rivers. For the forest, the complex uses an agriculture tower to grow it, which aids in purifying the air and psychologically aids in providing the people residing there a sense of serenity.

As with the other levels, it has a ceiling projecting an artificial sky and a river that leds to a waterfall used to generate electricity.

Toaru Majutsu no Index Light Novel Volume SS2
The district's ground level was where Kuruwa caught up with Hattori Hanzou on the first Friday of October, with the two ninjas clashing amongst the wind turbines.

Acqua of the Back Arc
The district was the site of Acqua of the Back and Kamijou Touma with Amakusa-Style Remix of Church's battle and much of the third level's interior was destroyed during the course of battle.

Honey Queen Arc
On August 5th one year prior to the main story, Item visited the district in a mission to infiltrate an illegal casino run in a former bowling alley by Honey Queen's support organization and gain information on their enemy,    entering the district at some point after midday and escaping around 6:30 PM. At time, the district's underground matched the sweltering heat of the outdoors but was shielded from the winds of the approaching typhoon (though Kinuhata Saiai thought about how it would flood if there was any trouble with the water pumps).

Trivia

 * Its borders are close to Touma's dormitory.