Rome IS eternal.
In hoc signo vinces.
Rome's legend is eternal. It's heroes renown is immortal. But Rome, and Romans, are dead, buried and gone. Just as all things will be. Even, I hate to say it, America eventually. But, again like all things, it'll rise again, greater than before.
And personally, I like my school's motto. "Deo Legi Regi Gregi." God, Law, King, People.
http://www.ukings.ns.ca/uimages/kings_crest.gif