Mysterious Arcologies
"A mysterious box of orbs have shown up at the captial building’s door step, turns out the orbs can be used to quickly deploy into a powerful arcology of different sizes."
Provides two types of arcologies at three different sizes, and are buildable only by the player (ai shouldn’t build them, though they will continue to use them from abandoned planets and planets they otherwise obtain). The arcologies provide a lot of housing, resources, increases in the number of districts, and other benefits! There is also now "automatic" versions that are without the housing and district increases (See screenshots).
Note: It also produces ACOT and Gigistructure Engineering resources. Additionally they reduce the district upkeep with strategic resources down to near zero (game doesn’t seem to let it go below 0.20 for upkeep).