The Underhive (of Tarvenhive)

I've been thinking a bit about the underhive lately, partly as a result of discussions over at Dark Reign.  In some ways I think this is the most difficult part of the Hive to deal with since the underhive has quite a strong character but getting that to work within a structurally sound framework is difficult.  I think I've just about managed it but I suspect this is one of the aspects of the hive that will be most subject to revision since it is, quite literally, the foundation of the Hive!

In terms of atmosphere/appearance I picture the underhive of Tarvenhive as something of a cross between Metro 2033 and the tunnels the ships use in the Matrix.  Anyway here's my vision of the structure of the underhive:

 

The Underhive

Though not officially recognised as a separate component of the hive the existence of the underhive is undeniable and it does exhibit a notably different topographical character from the rest of the Hive.  In comparison with even the poorest districts of the lower hive, the underhive is dilapidated.  Much of the underhive consists of warrens of tunnels that once formed parts of metro lines or infrastructure networks, some of the largest being former sewers.  As the hive has grown over the millennia so the primary utilities networks of the hive (water distribution and waste collection being most notable in this instance) have gradually risen as it is more efficient for them to be at a level closer to the point of use.  Since it is also more efficient for the utilities networks to share the same paths this leads to a particularly stratum in the hive which contains most of the primary utility networks.  Sometimes referred to as the ‘primary utilities layer’, particularly by administrators and engineers, this, for many people, serves as the dividing line between the top of the underhive and the base of the lower hive.  Indeed this is something of a self-fulfilling prophecy since one of the primary drivers behind raising a section of the primary utilities layer is high levels of vandalism and unauthorised tapping, typical of the lawlessness of the underhive.

   The tunnel warrens that form large parts of the underhive contain many sudden truncations and blockages, both from collapses owing to millennia of poor maintenance and from the driving down of foundation piles for new structures in the hive above.  Such foundation laying is, of course, done entirely without consultation with the residents of the underhive.  They can have some influence however in that the laying of foundations requires numerous expeditions into the underhive for surveying and construction and if the residents can put up a ferocious enough defence the architects may move a pile slightly.  Conversely construction of a new building in the hive also presents new opportunities for the underhive since as well as causing blockages due to foundation piles it can also open up new space, since few new buildings have any non-structural elements below the lower hive and often incorporate significant open space.  Such new spaces are prized since they are more structurally sound than older areas.  The primary structural elements of hive buildings are exceptionally strong and highly over-engineered such that major collapses in the higher levels of the hive are incredibly rare, but nearer the base of the hive, and especially in the underhive, there are many ad-hoc additions to the main structures with far lower construction standards.  It is these ad-hoc additions that are the primary cause of, and the worst affected by, hivequakes in the lower reaches of the hive.

   In addition to re-purposing and adding to existing hive structures the inhabitants of the underhive also sometimes actively excavate further into the bedrock below Tarvenhive.  Without the massive machines available to those constructing new structures for the hive above such excavation is very slow but nonetheless over the millennia substantial networks of entirely new tunnels and caverns have been constructed by the underhivers.  These tunnels and caverns are often associated with the more clandestine activities that take place in the underhive since even more so than the rest of the underhive their layout will be unknown to those that do not live in them.