Fordow Nuclear Facility is not only built 90m deep, but its main centrifuge halls are placed exactly under mountain ridges, adding additional several hundred meters.

It has at least 5 known entrances, two underground storages, and a vent that makes contact with the surface, making it the facility's weak point. It has a huge hall the purpose of which remains unknown, however it's also built directly under a ridgeline. A hardened structure likely serving as HVAC storage is located above ground.