Radiosonde Castle

Radiosonde Castle is a mysterious piece of landmass floating in high atmosphere and is the left over remnants of Star of Bethlehem. Its name comes from an observation equipment from Academy City called, "Mesosphere Radiosonde," because the two can float in the Mesosphere at 52,000 km.

Characteristics
A cross-shaped construction with measurements of length and width about twenty kilometers. The mass and density of the Castle is equivalent to an asteriod capable of bringing an ice age should it fall. 200 to 300 metal spheres are on the bottom of the Castle making it float.

Purpose
It is used by a magical organization that Leivinia Birdway refers to as "They" or "Them," to locate and chase after the Imagine Breaker of Kamijou Touma. "They" knew that Touma would eventually return to Academy City for even just briefly and that someone from either the Magic or Science side would attempt to safely land the Castle in the ocean. In order to do so someone would get on the Castle and have it break into much smaller pieces until it no longer possessed a global threat. Since the Castle is so large the pieces would eventually become bombardments dropping onto the city.