How to make a speical 3D map mode?

For my game i would like a tactical holographic map (in 3D) and at the press of a button the battlefield switches to this mode. What would be the bast way to implement this feature? one idea i had would be to make everything invisible except for the "holographic" models which would be made visible, kind of like a layer system as loading up a new level just for the map would be inappropriate for this kind of game. Any other ideas?