The Empire State

 was a tower named after the Empire State Building on Earth. It was just one big tower. It reached from half a mile underground to the upper part of the moon it was situated on's atmosphere. The people who founded it, manipulated the moons orbit, once it would have taken 2 years to get round all the six planets in its system it then just took over a week to do it. It became a famous trading post. (AUDIO: The Empire State)