In his incomplete historical Khokarsa cycle - Hadon of Ancient Opar (1974) and Flight to Opar (1976) - Farmer portrayed the "lost city" of Opar, which plays an important part in the Tarzan saga, in the time of its glory as a colony city of the empire of Khokarsa.
Farmer wrote Venus on the Half-Shell (1975) under the name Kilgore Trout, a fictional author who appears in the works of Kurt Vonnegut.