A crossover with an extemely obscure book from 2006 called, The Museum of Lost Wonder. A book where you are placed in a guided tour of a fictitious museum to explore and learn of an philosophical view of the world that once brought wonder and curiosity to many, but has been forgotten over time. "Here's a link to the site:" https://www.lostwonder.org/index.html
As usual, I would try to incororate it into the established lore so that it doesn't look like it just popped into existence without anyone knowing (tbh, it sorta does, but based on this origin video ).
Basically, it's a museum of lost and forbidden knowledge. hidden away from the world as in the past, ponykind was less open to other philosophies and wanted to destroy the museum due to it harbouring, "Heresy". It now only reveals itself to the extramely curious and those worthy to see this lost knowledge.
A secret society continues to curate and take care of the building and it's knowledge.
The basic gist of the story would be simple: an unsuspecting foal stumbling across the museum and going through a guided tour of it's exhibit halls.