Caves and indoor dungeons are almost always WMO files, which act as collections of smaller M2 model pieces. This basically means that caves and dungeons are created in 3D software like Blender, 3DS Max, and Maya, not Noggit.Outdoor dungeons (like Zul'Farrak, Zul'Gurub, and Black Morass) can be created in Noggit, however.