It's a fantasy role-playing game.

DM: You are Keyleth, a half-elf druid . You are the member of the famous group of adventurers. Previously, While he does this, he notices that there are three more opals embedded in the wall at shoulder height. Crouching under the opals, he makes it to the other side, he checks the door for traps, but finds nothing of interest, but notes that there is no handle or obvious way for it to open.
DM: Well as you can tell, there's the one in the center of the middle of the floor. Then there's one on the wall that he walked across, and as you to the other wall, there are another matching set of three on both walls.
Player: And they're all lined up.
DM: And they're all lined up. There's the two in the center of the room that match the one in the floor and then there's one to each side of that about four feet apart.
Player: Okay. I'm going to walk in a little bit. Are there any on the ceiling?
DM: Looking up. Make a perception check.
Player: Natural one.
DM: You get lost in the beauty of the structure.
