A circulene is a macrocyclic arene in which a central n-sided polygon is completely surrounded and fused by benzenoids. [5]circulene (corannulene), [6]circulene (coronene), [7]circulene, and [12]circulene (kekulene) have all been synthesized in the laboratory. These compounds belong to a larger class of geodesic polyarenes. Whereas [5]circulene is bowl-shaped and [6]circulene is planar, [7]circulene has a unique saddle-shaped structure (compare to cones and partial cones in calixarenes). Conceptually related compounds are the helicenes.