I voted both A Planetopolis City and A lifeless, war scorched world.
That's because in most of my games, it is between 2300AD and 2700AD... but some are placed in the approximate time-period of CT.
My TU has, instead of the OTU "collapse of the Vilani Imperium and establishment of the 2nd Imperium (Rule of Man)", the "Terran-Vilani Interstellar Wars" coming to a draw, with a negotiated Armistice establishing a neutral zone across the "waist" between the two rift regions... leaving the Vilani & Terrans in control of similar-sized territories.
Here, Terra is a Planetopolis... titular capitol of the Terran Confederation (but not the actual administrative OR military headquarters).
In the later games, Terra is a lifeless, war scorched world... because, in 2700AD (1660VI) the Armistice collapsed, and a renewed war raged across most of the space between Sol system and Vland. At the end of the Last Terran-Vilani War (2700AD to 2745AD), both polities were on the verge of military/economic/political/social collapse.
A Vilani task force had penetrated to Sol system and its commander, perhaps in accordance to his orders and perhaps out of hatred or desperation, ordered a total bombardment of Terra with all nuclear weapons in the fleet, as well as the directing of several comets onto impact courses. This, of course, rendered the surface blasted and radioactive. It also removed much of Terra's atmosphere, forever rendering it uninhabitable outside of sealed domes... which would be beyond the capability of the remnants of the TC for centuries.
This is because, as word spread of this act, Terran task forces all over Vilani space began retaliating in the same manner, which led to Vilani forces conducting more such attacks on TC worlds. This caused the total collapse of both interstellar governmental/economic structures... setting into motion the "Long Night". Many worlds had been "sown" with very long half-life radio-actives, to ensure they were never repopulated. Vland was one, with a return visit to Terra by the last operative Vilani task force in 2775 similarly poisoning Terra.
This is why it took so long to re-form interstellar "governments"... the majority of the important industrial & high-tech worlds had been utterly destroyed, and the survivors feared to let anyone else know they had survived, lest further destruction fall on them.
By the time of the CT setting, most of the universe has been re-ordered as per the OTU... save that a number of important worlds (including Vland, in addition to Terra) are shattered wrecks, with only symbolic artificial-habitat cities on their surfaces.