They had come into a broken bowl of hills—ragged, volcanic wilderness. A tropical paradise, dotted with tall watchtowers. At first sight they looked blankly harmless, like water towers. But the rounded storage tanks were armored pillboxes, ridged with slotted gun slits. Their gleaming sides were pocked with searchlights and radar blisters, and their tops were flattened for helicopter pads. Thick elevator taproots plunged deep into the earth—no doors were visible anywhere.