India, Sept. 5 -- It was a bunker made of reinforced concrete and steel. It was half underground, and camouflaged with mud, leaves and grass. Just beyond this innocuous-looking mound was a waterbody about the size of a large swimming pool.

Ahead of it, we could see an African tusker making his way to the pond.

"Hurry, the animals are already here. We are late," said our guide, as he opened a metal door to reveal steps leading down into a dark chamber.

We emerged, curious and a bit nervous, from our safari jeep. One by one, we entered this man-made cave. It was surprisingly roomy inside, with a modern toilet to one side.

Our guide slid open steel windows all around the room, each 2 ft tall and at eye level. There were no grills or mesh...