The Tower is a collosal, pillar-like tower on which the girls of Team Dead or Alive and Team Final Fantasy fight.
Featuring a stone temple at its apex, the girls are forced to continue their fight while descending the tower's sheer face after Ayane forced the group to jump over the edge after destroying the Temple.
Eventually the tower itself is destroyed after Rachel, who had been perched with her War Hammer on the tower's face, hit the tower with enough force to demolish the construct.

The tower seems to be at least 6500 meters or over 21000 feet high (considering they are mostly in a state of free-fall for a little longer than 2 minutes).