The underworld of the K'iche' Maya, ruled by death lords who lose at ball games.
Documented
The Popol Vuh record
The K'iche' epic, transcribed in the colonial period and translated most famously by Tedlock, narrates the Hero Twins' descent through Xibalba's houses of knives, jaguars, and bats, and their victory over the death lords.
Assessment: Documented in the surviving text and corroborated on Classic-period painted vases a thousand years older.
Stories
The ballgame against death
The story's engine is sport: the underworld summons the twins to the ballcourt, as it summoned their father and uncle to their deaths. The twins cheat the traps and rig the final game.
Assessment: Folklore with a rulebook. The ballgame was real, the courts stand in the ruins, and the story made it sacred.
Interesting claims
The caves were the set
The claim: deep cave systems like Actun Tunichil Muknal functioned as literal entrances to Xibalba, staging grounds where priests walked the myth. Bones and offerings in the dark chambers are the props.
Assessment: Caves as ritual portals are archaeologically documented. Identifying any cave as the Xibalba is interpretation, not inscription.