You can underlay 2D geometry objects stored in DGN files created with MicroStation. Underlays are similar to attached raster images in that they provide visual content but provide some object snapping. Unlike external references, underlays cannot be bound into the drawing.
DGN support is limited to V8 DGN files and 2D objects. The 2D objects will be imported or attached with full (X, Y, Z) coordinate information, as was present in the original file. If 3D solids, surfaces, or other 3D objects are encountered, a warning message will be displayed about 3D content found in the file, If no 2D objects are encountered, and only 3D objects are present in the file, a warning message will be displayed.