Echo echo_oche: only knows the Dollhouse
Jean-Claude masterofstlouis: Paris, of course. Also Rome and Prague.
Nikola Tesla (the time traveler, not the vampire) niko_tesla: On Earth/present, New York City and Sydney. Elsewhere/when, Tranquility (first settlement on the moon), and of course his home on Harmony.
Gaius Baltar nomorenicegaius: Caprica City
David Xanatos selfmademadman: New York City
The Doctor thedoctorwho: On Earth, London (obviously), though nothing is as grand in his mind as the Citadel on Gallifrey.
Kitai wantedahorse: Would rather avoid cities altogether
Agnes Nitt witchoftwominds: Still has a longing for Ankh-Morpork

(feel free to leave notes for any of these as well...)