Thousand Yard Stares: Ruins and Ghosts of the Battle of Peleliu, 1944, 2008 (Thanks, Alex!)
Unlike previous battles in the Pacific, the Japanese didn't place the entire emphasis of their strategy on defending the beaches - they fortified the island, in particular a mountain called Umurbrogol. The Japanese riddled Umurbrogol with a huge network of caves and tunnels from which to operate (this image shows a plan of one complex). Once they had completed their work, they evacuated the civilians, and waited for the Americans.
Below you scan see the entrance to one of the Japanese caves, and beneath that, a shot from inside, looking back to the entrance. The entrance itself probably isn't more than 3 or 4 foot high; inside the cave ceilings are slightly higher, although very uneven - but it's not a great place to be when, like me, you're 6 foot 2. It was a horrible place to spend 15 minutes, but caves like these were where the Japanese forces lived for the two month duration of the battle of Peleliu. Inside, you can still see discarded boots, bottles and bullets.