"Mekett architecture revolves around the physical hive, something which Mekett actually call I'kaya, or home. The use of the word hive is an external construct equating them with insects. Most Mekett hives began with the sleeping chambers from which they emerged. Collectively, these were called the Constellation. Post-emergence, these subterranean structures acted like nurseries for the new communities that provided shelter, storage, and defense. Hives have typically branched out from the Constellation node.
It is not correct to characterize a Mekett hive as an underground structure since most large buildings exist above ground. However, entrances are almost always below ground, and few roads exist on the surface. Mekett typically travel using below-ground streets (these are not narrow tunnels). There, buildings have entrances like any other. There are rarely windows near ground-level, and even those above are small and utilitarian. One may enter a building without ever even realizing they have traveled above ground. If it was economical for large structures to be built below, they likely would be. A side benefit of this is security. Entrances that go to the sub-streets are wide, well secured, and few.
The Mekett style is actually fairly decorative and attractive. This is not so much a matter of natural tendency, nor does it reflect their usual efficiency, rather, they are mimicking the Meraic designs that they see in illustrations and on murals. Meraic design favors strong contrast, surface ornamentation, and often employs shapes that flow with, mimic, or stand out from the land around them."
https://wiki.massivecraft.com/Mekett_Economy_and_Technology