Portal to Ispar
From Drunkapedia
In a patch several years ago, there was a floating fortress that floated above the surface of Ireth Lassel. It was unreachable to the regular adventurer, and contained a portal that read "Ispar."
If someone exploited and went up there somehow, walking into the portal would cause the adventurer to fall off the edge of the map and fall forever into utter oblivion. The portal was meant as a display only; not meant to travel through.