This is the first campsite on the way to Son Doong, just within the entrance to the Hang En cave. The trail leads down the rock slide you see in the foreground to the wooden bridge on the lower right. To get to the campsite, you wade across the underground river.
In the rather elaborate campsite itself, if you look closely you can see the tents of the paying participants in a line on the left, the dining pavilion in the center, and the cooking cluster of the porters on the right. The trail onward and through the Hang En cave leads along the river the curves to the right, and into darkness.
I made this photo with the late afternoon light coming through the cave opening, on my way down to the campsite and to a much needed swim in the lake!
Exposure info: Nikon D810, Zeiss 15mm f/2.8, five combined exposures with each exposure at f/8 and ISO 250, exposure times from 2 seconds to 30 seconds; tripod mounted; processed in Nik HDR Efex Pro and Photoshop.