Purgatorio, also known as the Meta-World, is a secondary dimension in Umineko no Naku Koro ni, separate from physical reality. Purgatorio is seen as the witch's realm and is where the "games" of Umineko no Naku Koro ni take place. Any fragment of reality may be viewed from Purgatorio. It is implied that Purgatorio is some kind of afterlife.
Purgatorio seemingly appears in Higurashi no Naku Koro ni, specifically in Minagoroshi-hen as the Time Void. In the opening scene of Minagoroshi-hen, Rika Furude is seen examining several different fragments in a Purgatorio-esque place before finally entering one.
In Ougon Musou Kyoku, either team may attempt to enter Purgatorio for significant advantages and powerful moves.