Ancient shrine
Ancient structures are large rooms that contain at least one ancient cryptosleep caskets and bug hives or mechanoids. Due to being fully enclosed, one cannot see within the room, and hovering over the grayed out area as seen in the picture will only say 'Undiscovered' in the bottom left corner.
They are built mainly out of stone walls.
Rare things and artifacts, such as luciferium, psychic insanity lances or psychic animal pulsers can be found in these buildings.
They can spawn on any map tile, and can sometimes have multiple, or none at all.
Cryptosleep Caskets
Each casket contains a human belonging to the spacer faction. The human can be neutral or hostile to the players, and can also spawn downed or dead.
All pods in the ancient structure open simultaneously. When done so, downed or dead people will fall out of the casket right beside it, while others will start to walk around, escape to the map edges or converge on your colonists.
Pod people wear synthread and hyperweave clothing. They can be equipped with a weapon, and sometimes come with plasteel, components, and gold, which drop when they are downed.
Having a colonist walk to the walls of the structure will cause this prompt:
"As (Colonist Name) draws near the ancient wall a sense of foreboding overcomes him. (S)He isn't sure why, but (s)he feels this dusty structure may contain great dangers"