|“||The XCOM project's headquarters are currently situated deep underground. After building multiple facilities, it will become necessary to evacuate further. Please note: As excavations reach deeper beneath the base, the cost of these expansions will increase accordingly.||”|
– XCOM Database, XCOM: Enemy Unknown
Prerequisites: Adjacent building square that has been excavated.
Time to Build: 5 Days
Facility Maintenance: None
There is no difference in the cost of excavation between game difficulties.