With the Walk tool, you can navigate through a model as if you were walking through it. Once you start the Walk tool, the Center Circle icon is displayed near the center of the view, and the cursor changes to display a series of arrows. To walk through the model, drag in the direction in which you want to move.
When walking through a model, you can constrain the movement angle to the ground plane. This enables you to walk around while maintaining a constant camera viewpoint elevation. If the walk angle is not constrained, you "fly" in the direction you are looking.
As you walk or "fly" through a model, you can control the speed of motion. Speed is controlled by the distance the cursor is moved from the Center Circle icon, and the speed setting.
As you use the Walk tool, you can adjust the camera elevation by holding down SHIFT. This action temporarily activates the Up/Down tool. With the Up/Down tool active, drag up or down to adjust the elevation of the camera