Tower of London

Tower of London (処刑塔 (ロンドンとう) ) is a historic castle in central London, England. In the Toaru Majutsu no Index universe, it is still used to keep prisoners despite being a tourist attraction.

Principles
Historically, the facility was one known as a facility of blood, torture, and execution for prisoners. However, the Tower of London today is open to the public for just under 14 pounds. There, the facility displays historical execution devices as well treasures of the Royal Family.

Despite this, the facility is still being used for its original purpose due to the blind spots in the building. Prisoners were still kept there and they were tortured or executed without hesitation as needed. If one entered through the normal entrance, those shadowy portions were completely unreachable. If one entered through the secret entrance, one could not escape the shadowy portions. These blind spots, unlike the areas where the sightseeing were held, were cramped and dark.

Seven Tools of the Tower of London
Kanzaki Kaori mistook the various tools of Misha Kreutzev as the Seven Tools of the Tower of London (処刑塔の七つ道具(ロンドンとうのななつどうぐ)) after looking at her. They are apparently famous interrogation tools used in the Tower of London. Since Kanzaki mistook the tools on Misha's person as like that of the Tower of London, it can be assumed that the tools include pincers, hammers, an L-shaped crowbar, saw, and a screw driver.

Academy City Invasion Arc
Lidvia Lorenzetti was mentioned being kept in the Tower of London.

Document of Constantine Arc
Stiyl Magnus, along with Agnese Sanctis, went to the tower to interrogate Lidvia Lorenzetti and Biagio Busoni regarding God's Right Seat. While Biagio remained defiant, Lidvia asked about what is happening outside. Stiyl said that she can make a guess on what was happening outside. She then shocked them by offering what she knew in exchange for have everyone that worked for her currently being held in the tower released.

Toaru Majutsu No Index SS: Kanzaki
It was mentioned that if Kanzaki took out Leivinia Birdway and moved her to the magical prison within the Tower of London, the world's safety would increase by a few percentage points.

Magic God Othinus Arc
Acqua of the Back commented about the second princess Carissa and the Knight Leader having both been held in the tower for their action involving the British Halloween following World War III and have been temporarily released for the emergency situation for a preemptive attack on GREMLIN.

Return to England Arc
During the invasion of the United Kingdom by the Crowley's Hazards, in order to neutralize the final barrier protecting London, Aleister Crowley engineered Kamijou Touma's capture by the Knights of England so he would be sent to the tower and be in a position to destroy the core of the barrier there. Following an interrogation by Stiyl Magnus, Touma managed to escape with Othinus's help and destroyed the core.