Fantasy and sci-fi are replete with underground cities: Ember, Zion, Menzoberranzan, Khazad-dûm and more. But are there any caves on Earth that are large enough to actually contain a real, functional city?
Nicholas Jackson over at The Atlantic has a great piece about the tear down of the Zion nuclear power plant in Illinois that was permanently deactivated in 1998 after both of it's reactors were accidentally/coincidentally shut down. But even when done properly, complete removal isn't so simple.
Here's a Lego diorama of one of the best scenes of Matrix Revolutions: Zion's last stand against the Matrix, humans in their mechas against merciless Sentinels. The close-up of the human resistance mecha begs for an official Lego version.