The Tower of Babylon is one of the nine legacies that was left behind by the genius professor Regina Babylon. It was created during the period of the ancient Paruteno Civilization approximately 5000 years ago. It was later discovered by Touya Mochizuki and is managed and controlled by the gynoid Pamela Noel. It is the sixth piece of Babylon to be discovered and had already docked with the Rampart due to it's teleportation circle being destroyed by an erupting volcano 527 years before it's discovery.
The Tower of Babylon serves as the power source for the combined Babylon. It's primary function is the absorption and the amplification of magical elements in the atmosphere, the energy collected is used to power the various facilities of Babylon. Each of the other pieces of Babylon have similar devices installed as well but even combining the output of the other eight pieces wouldn't even come close to the energy produced by the Tower. The output of energy created by the Tower is such that it is essentially the heart of the united Babylon. By channeling the power collected in the Tower to the other Babylon it is possible to increase the output of their respective functions (The amount of products created by the Workshop can be increased exponentially). 
The original location of it's teleportation circle was at or near a volcano in an unknown country. The test to activate the circle itself is currently unknown because it was destroyed.
The Tower requires the least amount of maintenance of all the Babylons
It's teleportation circle was the only one to be destroyed before Touya could locate it.
It along with the Rampart are the only pieces of Babylon to be able to dock on their own 153 years after the destruction of it's teleportation circle.