Nova Roma first appeared in New-Mutants #9. It was a remote city hidden in the Amazon that had never moved past ancient Roman times. When it was found, Nova Roma was undergoing a power struggle between the father of Magma and the husband of Selene. The New Mutants resolved this, and found out that Selene was a mutant. Later, when Magma returned to Nova Roma with Empath it was believed that the city was not in fact descended from ancient Romans and that Selene had captured many Europeans, and put them under a spell to make them believe that they had grown up in Nova Roma as an attempt to recreate the times that she loved best.
When Empath realized that the spell was wearing off, he put all of Nova Roma's citizens in to a trance, for fear of losing a place he had deemed his home. The trance ended in New Warriors #31 when Cannonball, Firestar, and Warpath came to Nova Roma to deliver news of the Hellion's death.
Later it was revealed that an unidentified agency had altered the Nova Romanii's minds to make them believe they were not original descendants of the old Roman Empire but with time their mind were restored and many citizens returned to Nova Roma.