DLC1LD Quest Holding Cell is a test cell that is accessible only through the use of console commands. This cell is comprised of Soul Cairn-esque architecture, and while unusually large, is completely devoid of life.
The cell is larger than most test cells, and its stone, rubble-covered floors contain a number of piles of non-interactable bones, and a few dead trees, along with several staircases, arches, and immense towers which can be climbed.
A relatively short distance directly underneath the spawning area is a small, empty, cave-like room with a tall opening facing east-west. The cave has a dirt floor and the walls are made of stone, with moss and vines growing out of them and the ceiling. It can be reached by clipping through the floor via the console command
tcl or by falling from the closest point to the spawning area.