High society's upper echelons within Nakarta, available only to the super-rich that are often ignored by the police due to being paid off by many individuals within it. It's only called the 'Overgrowth' by those that know of it and it's mostly used to make fun of the fact common society only thinks the 'Undergrowth' is the only place crime truly happens in.
Many of high society's overly-rich or royalty exist here in odd secretive events. There's no easy way in, and no one from the outside of this group gets in. It's mostly company CEO's or politicians that partake in the parties.
Silver de la Corca is often shunned for his lack of interest in partaking in parties he doesn't host, especially considering it's been twice now where he's hosted a party someone's died at.