You can select the pivot point around which to rotate the model, using the Center tool
The point of the arrow indicates the point at which the model will be centered.

The point defined by the Center tool provides a focal point for the Zoom tool and a pivot point for the Orbit tool.
(), or select it from the Navigation bar.
from the ribbon or the Navigation bar to rotate the model with the new center of rotation.
from the ribbon or the Navigation bar to zoom in on the model about the new center.
Zoom tool or the
Orbit tool to reorient the view of the model. If you are using one of the Full Navigation wheels, hold down CTRL before using the Zoom tool.