The tower belongs to Madame Shhh and is situated towards the back of Bubble Land. HJ5 uses the needle at the top to puncture a hole in their containment bubble and effectively pop all the containment bubbles in Bubble Land.
The tower itself seems to be relatively small and has know noticeable features other than being surrounded by a few bubbles on each side and a giant disco ball towards the top. The interior is never shown.
Top of the tower with HJ5 in the bubble and squirrels on scooters in pursuit.