This is a wall walk exploit that you can do in the Accretian HQ. Its a video:
What you do basically is go to the banker in the HQ, go into walk mode and keyboard mode, go in to the corner of the boxes on the right hand side, turn to the boxes, and walk into them. Once your on them walk on top of the box thats on the boxes. Once your on that, face the wall and walk into it, you'll teleport to the top.