Giant Hollow Fortress

The Giant Hollow Fortress is a floating structure commanded by the Unnamed Female Arrancar during an attempt to attack Karakura Town. Its core is the most powerful part, as well as the most fragile.

Overview
This Fortress is made up of hundreds of Hollows, merged together, thus creating a giant Hollow-like building. The fortress is later destroyed by Urahara Kisuke's Benihime, after the Karakura-Raizer Team prevent it from destroying Karakura Town, leaving the full extent of its powers unknown. The Unnamed Female Arrancar perished within the Fortress.