What is the main setting in the novel, Heads?

The events of the novel, Heads, are set on the moon about two centuries in the future. It is inhabited by two million people, all allied with one of more than fifty families, called "multiples." The major action takes place in the Ice Pit, "a volcanic burp in the Moon's ancient past, a natural bubble almost ninety metres wide that had once been filled with the aqueous seep of a nearby ice fall."