Branch Cities

Two or more distinct cities co-located.  The term originated before Terran contact, but is also now used by Symbians to refer to a Symbian city and a Terran city located in the same place (e.g. Angelic, Calis, Symbia and Los Angeles, California, USA, Terra). The original meaning referred to a difference in habitat, usually by height; a city with a substantial ave population may choose to build tower sections inaccessible except by flight, and keep to those. 
Notable among branch cities is the triple city Aja, in the province of Ajatos in Forestis, which has Ajalto in the rain forest canopy, Aja at ground level, and Ajabas in the caves 200 meters below ground level. Ajabas is connected to Aja only by a single cabled lift for visitors, and Ajalto is inaccessible except by flight.