The siib is a common architectural feature of much of the Beyond.  On Qat, except for  Port
Sawreven and the trade villages, it is the dominant building type on Qat.  So here would be a
good place to discuss the siib.  

The siib, to generalize is an underground building complex, often with hidden and multiple
means of entry.  Siibs can be straight forward, a underground house with one or two escape
tunnels.  The entrance can be a straight tunnel to the house itself or a tortuous tunnel with
numerous doglegs, dead ends, and set with traps.  On the extreme end of the scales siibs  are
massive underground complexes complete with quarters for dozens or even hundreds of people
covering several kilometers.  
Eight Factory Siibs were built between 898-914 as part of a IISS plan to decentralize
manufactoring with the increase of attacks on Qat.  Abandoned by the scouts when
they left, they are now in the hands of several of the local families.
Simple Siibs are usually one level units housing
families.  Entrances tend to be camouflaged
hatches either built into the ground of part of an
out building.  Any vehicle hangars are built
anyway from the main siib & connected by
tunnels.  Missiles are the usual space defenses
for this type of siib. House defenses usually
consist of boobytraps as most landholders depend
on stealth & discretion.  If that fails, every family
keeps an arsenal.
Multistory siibs on Qat can have 2-10 levels & are either communities or the domiciles of some of
the richer citizens of Qat. Most designs are built in the native stone of the planet or utilize caves.
Layout usually include living quarters on the upper levels with powerplants, hangars,
workshops, & marketplaces in the lower levels.  Some siibs will add a security level on the top
floors.  Most of these siibs have extensive land to space batteries built 1-3 kilometers from the
siib.  Land defenses consist of underground bunkers armed with a variety of weapons or weapon
turrets salvaged off ships.