There is a small toolbar top left of each views:

The tools are:
Opens the view configuration window
(same as pressing the 'O' key).
When the point of view in a view is rotated, it is around a center.
The center is defined by the next 4 tools:
Rotate the point of view around the world center
Rotate the point of view around the selected mesh center
Rotate the point of view around the selected items center
Rotate the point of view around the one camera 'point to' center.
The next 4 tools opens one change point of view tool:
Rotate the point of view using view coordinates:
Rotate the point of view using world coordinates:
Move the point of view:
Zoom the point of view:
Lock the point of view. In perspective mode, the point of view can not
be moved, rotated or zoomed. In isometric mode, the point of view can not be rotated, but can be moved or zoomed.