The following tip came from EatYourCAD.com: MicroStation has an option that automatically forces 3D DWG files to be opened in 2D. If you don’t know this option is turned on, you may be very surprised to find all your 3D DWG files — including ones you just saved from a 3D DGN file — flattened down to 2D!

Here is how to turn this option off:
1. From MicroStation Manager or the Open dialogbox, select a DWG file.
2. Click on <DWG Options>.
3. Uncheck the box for “Create 2D models for Model Space”.

Untick the box to open your DWGs in 3D.

That’s all there is to it.
Run by day-to-day users in the CAD industry, from CAD manager to CAD consultant to CAD
user, EatYourCAD.com is a bountiful resource of tips, tricks and educated opinions that should be on every CAD user’s “must visit regularly” list.

Thanks, EatYourCAD.com!