School District 21 (第二一学区 Dai Nijūichi Gakku?) is the westernmost School District of Academy City. It is bordered to the east by School District 9, to the north by School District 17, to the south by School District 13, and to the west by Western Tokyo.
Unlike School District 23, which is flat due to its many runways, School District 21 is a mountainous area. The mountainous area holds many dams that act as the city's water source. The water is distributed to the whole of Academy City using pipes, from uses such as beverage service to industrial use. The stars in the night sky can be seen more clearly in the district than the rest in the city. Perhaps because of this, the district contains several astronomical observation facilities. The area is also the location of an experimental geothermal power station situated on the mountain's peak, and a large-scale meteorological observatory, which is also the base for the disaster recovery group Useful Spider.
The district also keeps wilds animals due to its mountainous area.
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Toaru Majutsu no Index
- Main article: DRAGON Arc
Shinyaku Toaru Majutsu no Index
Kamisato Rescue Arc
- Main article: Kamisato Rescue Arc
|5th Emergency Treatment Center||Medical Facilities|
|Ground Geo||Power Station|
|Matsuo Ryuusuke's log cabin||A log cabin near Ground Geo which acted as a secret hideout for L.S.S. president and Biohacker Matsuo Ryuusuke, and contained many of his created specimens. Destroyed by the Beginning Child after her awakening.|
- Toaru Majutsu no Index no Subete: Map of Academy City
- Toaru Majutsu no Index: Road to Endymion Chapter 4 Part 2
- Toaru Majutsu no Index no Subete
- Toaru Majutsu no Index: Mars SS
- Shinyaku Toaru Majutsu no Index Light Novel Volume 11 Chapter 1 Part 2
- Shinyaku Toaru Majutsu no Index Light Novel Volume 17 Chapter 3 Part 4
- Toaru Majutsu no Index Light Novel Volume 19 Chapter 3 Part 3
- Toaru Majutsu no Index III Episode 16
- Toaru Majutsu no Index SS: Biohacker Arc Chapter 5