We were well into the Yucatán now, on a secondary highway that would take us to Mérida. All around us was flat, sun-baked desert—a vast expanse of scrub-dotted limestone and yellow soil, unbroken by rivers or lakes. The only "hills" in the region were the ruins of ancient cities—bleached mounds of rubble that mark where a building or temple once stood. The other landmarks were of more recent manufacture—power lines, oil rigs, razor-wire fences that marked the edge of civilian no-go zones, and the occasional radar dish or military landing pad, surrounded by security fencing and low bunkers that I guessed held light tanks, troops, or LAVs.