Floor 0502

Floor 0502 was a floor on a Mondasian colony ship.

Like Floor 0507, it served as a solar farm, albeit a smaller one, and had a windmill. Its landscape was also very similar to that of Floor 0507 prior to the latter floor's destruction, resembling a spring countryside.

Shortly before the Battle of Floor 0507, the Twelfth Doctor explained to and  that he intended to evacuate the children and most of the adults of Floor 0507 to Floor 0502. During the battle, when the Cybermen retreated from their initial attack to prepare for a bigger assault, the Doctor ordered Nardole to lead the evacuation, stating that there would be enough livestock in the cryogenic chambers for them to survive; despite his reluctance to leave the Doctor to destroy the Cybermen, Nardole complied. Shortly before the destruction of Floor 0507, Nardole, Hazran and Alit successfully evacuated with the other children to Floor 0502 via the lifts; Nardole later waited outside the lifts, sadly confirming to Alit that the Doctor and Bill Potts were not coming back from Floor 0507. Nardole then explained that the Doctor had destroyed most of the Cybermen, granting him "a while" to calculate another plan before the Cybermen remaining on Floor 1056 attacked again. Nardole then walked off with Alit and another child to have food with Hazran and the other children. (TV: The Doctor Falls)

Behind the scenes
Although Nardole never mentions Floor 0502 by name when he appears to the Twelfth Doctor as a glass avatar in PROSE: Twice Upon a Time, it is possible that Nardole spent the rest of his life onboard Floor 0502, as he states that he lived "happily ever after" onboard the Mondasian colony ship. If so, then the attacks by the Cybermen that Nardole mentions, as well as the subsequent annual Cybermat incursions, may also have occurred on Floor 0502. It is also possible, as a result, that Nardole's experiences that he details in his space-time telegraph to Bill from the Mondasian colony ship in WC: The Best of Days also occurred on Floor 0502.