Shadows and silhouettes are potentially interesting because of their graphic impact.  They appear straight-forward, even simple, at first glance.  But as with everything else photographic, the seemingly simple image may be ambiguous upon consideration.  

At the least, the partial silhouette can imply the whole. Someone seeing this segment doesn't need to see the entire structure to know with certainty it is the Eiffel Tower.  They do not say, "That is a picture of the Eiffel Tower."  They say, "That is the Eiffel Tower."

Empty chairs always seem to convey some message.  Here the chair itself is a minor part of the photograph.  It is the shadow that claims prominence.  The simple message is this: "Here is a chair."  A more subtle message is this: "This shadow is as substantial and real and important as the chair itself.  We can't sit on the shadow, but we can see and appreciate it."   The chair's utilitarian function (supporting someone) is not depicted, and barely implied given that only a small part of the seat is shown, and that part is empty.  Indeed, the shadow confirms that the seat is completely unoccupied.  But there could be more.  A chair in the public square of a Tuscan village on a sunny late afternoon invites use, by visitors or the residents gathering before evening falls.  It is empty now; it probably won't be empty for long.  

Iconic landmarks don't have to be brightly sunlit to be identifiable.  They are more interesting when their shadowed surfaces are not plainly revealed, and only hint at their details.

This is a hybrid; silhouetted after sunset, the trees provide context and support for this Tuscany streetlamp.  The warm brilliance of the globes depicts one stage of the transition from sunset to early dusk to late dusk and then night.