Common Lisp dynamic variables

One thing that Common Lisp has which is very powerfull is its dynamic variables. The following code ilustrates the concept:

CL-USER(124): (defvar *x* "Hello") ; *x* is a dynamic variable*X* 
CL-USER(125): (progn
                (let ((*x* "Ola")) ; establishes a dynamic environment for *x*
                  (format t "~a~%" *x*)
                  (setf *x* "Ciao")
                  (format t "~a~%" *x*)) ; end of the dynamic environment
                (format t "~a~%" *x*)) ; back to the initial dynamic environment
                                       ; *x* assumes its original binding 
Ola 
Ciao 
Hello 
NIL 
CL-USER(126): 

Now if this is used with multiple processing and/or closures you get very powerful ways to separate things and a great amount of flexibility almost for nothing.