Benzo[i]naphtho[c,d]bicyclo[5.4.1]dodecan-12-one.

In the title compound, penta­cyclo­[11.8.1.13,11.07,23.015,20]­tricosa-3,5,7,9,11(23),15,17,19-octaen-22-one, C23H20O, the bi­cyclo­[5.4.1]­dodecan-12-one moiety takes a rigid conformation in which the seven- and eight-membered rings take chair and boat–boat forms, respectively. The mol­ecule has a non-crystallographic mirror symmetry perpendicular to the benzene and naphthalene planes.