The world is three dimensional.
These are three views of an object: from the front, the top, and the side.  The object was once commonly found on commuter trains.  What is it?
These are the  top and front blueprint views of an object.  There are no hidden lines and no curved surfaces.  What is the side view?
These are three views of an object carved from a block of wood.  How can that be?  Where might you find such an object?       (An Eternal Golden Braid.)
 
 
 
The top object is a paper Dixie cup.  This type was made to be folded flat and placed in dispensers next to the water coolers on passenger trains.
The carved wooden object can be found on 
the cover of the book by Douglas R. Hofstadter, 
Gödel, Escher, and Bach: an Eternal Golden 
Braid. (Vintage, NY 1979.)