Symbol of the trinity. Found in Celtic ornaments, Germanic runestones, Japanese drawings and Christian imagery. Everything is interconnected. The Stranger pins a drawing of the triquetra on the wall of Room 8 in the hotel. It is on the covers of books belonging to Noah and Claudia, and on a metal trapdoor in the middle of the cave.
The triquetra symbolizes the interwovenness of the three timeframes connected by the wormhole in the cave: 1953, 1986 and 2019.