Worst-case scenario: the UEd Goblin wipes the map and burns down your house.
Legacy:Manipulating Terrain
From Unreal Wiki, The Unreal Engine Documentation Site
Rotating and Mirroring Terrain
Rotating
- With the existing terrain, select the terrain info actor.
- Go into the TerrainInfo Dropdown section.
- Go into the TerrainScale struct.
- To flip the terrain, put a minus (-) sign in front of the values of X and Y.