"Closed rings consisting of benzenes are called circulenes. [5]circulene (corannulene), [6]circulene (coronene), 
[7]circulene[1] and [12]circulene (kekulene) have 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."