Phobos

The (now) only moon of Mars. It has become a port for countless ships that either trade with or transport people to Mars. So much so that it is now at a point that Phobos is now twice its original size from the construction of the extensive networks of shipping platforms. Large ships that aren't designed for atmospheric flight use Phobos as an intermediary to shuttle goods and passengers to and from Mars.
Since the moon has a myriad of structures that have built up and up over time, there are many areas down below its infrastructure that are now unused and forgotten. Perfect for the shady type to take advantage of.

Type

Planetoid / Moon