At one point in the game, the player and their four diving partners get trapped in this room by Okeanos's Guardian and its Goblin Sharks. However, the player can use the song of the Dragon Flute to escape, but they also open the Treasure Room in the process, and the Song of Dragons produced by the Flute also drives the Singing Dragons mad, causing them to go into a rage and collapse the Cavern of the Gods.
The Mausoleum has two entrances, one in the ceiling of the Pillars of Shadow and the other in the ceiling of its twin room, the Pillars of Light. The player must solve several puzzles to get to either of these entrances, however, as there are multiple locked doors painted with murals that the player must unlock first, as well as several other side puzzles.
It is located on the map spanning across coordinates B-2, B-3, C-2, and C-3, smack-dab in the middle of the Cavern of the Gods.
The room contains three carved pedestals, which depict a ram, scarab beetle, and hawk. The walls are covered in artwork reminiscent of ancient Egyptian stylisation.
In the player's notebook, the Celestial Mausoleum is described as follows:
"This is the most impressive room in the Cavern of the Gods. What exactly did these ancient people want to convey to us through these mysterious murals?"