Beehive

Beehive (蜂の巣) is a grim-looking location filled with small multi-tenant buildings in Academy City's District 7.

Principles
Officially, the area where the Beehive now stands is supposed to be rented out as business facilities. However, due to the tenant review process being lax, tenants with suspicious backgrounds have been using the place. The Beehive is a perfect hideout as result of the lax standards. Moreover, they are used by girls who have run away from home use the Beehive as cheap apartments, used as cages for dangerous pets, used for workshops, and cults not recognized as proper religious organizations use them as their home base.

According to Kamijou Touma, people can easily obtain a lease just by visiting a website, and that people running it often did not know who was using the rooms or for what purpose. There are apparently cases where people would break into empty rooms to use them without a lease.

Toaru Majutsu no Index: Road to Endymion
The Gate of the Gods Come from the Heavens use one of the buildings in the Beehive as base of their operations, as well as the center of their Agni's Festival Fire spell. Stiyl Magnus later discovers the building, and ignites it with his rune card. Touma and Index also come upon the base much later, and later destroy the center of the spell, but to no avail as the center has been moved to another place as soon as Touma destroyed it.

Sozty Exica, a member of the magic cabal, stays behind to protect her group and an ensuing battle with a modified version of Agni's Festival Fire takes place, causing much havoc.