The village chief had been out in the jungle for days, but his wife was home. She welcomed us warmly as a gaggle of children played at her feet. Walking outside, she began to address us, via Binh’s translation: Of the dozens of ethnic groups in Vietnam, “we are the poorest!” she exclaimed, nonetheless smiling broadly. In reply, and in a classic demonstration of Vietnamese frankness, Binh bluntly put it to her that perhaps they ought to move somewhere offering more forgiving conditions. At this, her smile vanished. “Here we have land!” she countered, jabbing her finger at the dry terra-cotta earth. “We can’t farm rice, but we can farm corn, fruits and we can fish, we can hunt. Where would we go? What would we have if we moved?” Then, as abruptly as her temper frayed, her easy grace returned as she swept a crawling child into her arms and took a seat back in the shade.

As we pushed on, the valley opened up farther — magnificent, lime green hills rising all around us. A couple of miles later, one of the mighty arches of Hang En cave came into view.

After forging deep into the cave, still following the Rao Thuong River and clambering up to the lookout point with its views over the beach campsite, we headed down to the tents where we dropped our gear. The river we had followed carves right through the cave for over a mile, finally emerging in another valley on the far side of the limestone massif. We followed the water, first into darkness and onward into gradually strengthening light that built to reveal another mountain of rocks towering over us. Again we climbed, this time reaching a vantage point that gave us our first sighting of the most colossal of Hang En’s arches.

At almost 400 feet high, its scale is spectacular — it’s so large it could almost accommodate the Statue of Liberty. Looking down at the floor beneath it, we watched as young boys scurried back and forth. “They are picking up infant swifts to take home and cook and eat,” Binh said. “The recently hatched birds either attempt to fly and can’t, or they simply fall from the nests.” At this time of year the birds are easy prey, but when they aren’t falling, the boys scale the arch using ropes to fetch them directly from the nests. When we reached the bottom they proudly showed us their day’s haul, the swifts clinging to their T-shirts.

Ravenous, we made our way back to the camp, our bright orange tents now illuminated by lamps as dusk fell outside. We shed our sodden clothes and took a dip in the warm water of the turquoise pool as the porters finished preparing dinner.