 Although the oldest example dates back to the 5th century BC, it was only in the wake of the influential design of Trajan's Column that this space-saving new type permanently caught hold in Roman architecture.Apart from the triumphal columns in the imperial cities of Rome and Constantinople, other types of buildings such as temples, thermae, basilicas and tombs were also fitted with spiral stairways.Their notable absence in the towers of the Aurelian Wall indicates that although used in medieval castles, they did not yet figure prominently in Roman military engineering.