The fine tomb of one of the family of the Aterii found at Cento Celle, and now preserved in the Lateran Museum, is covered with panels of sculpture of numerous buildings packed closely together, of which there is reason to believe some are only designs, and were never executed. This makes it probable that it was the tomb of an architect, and one of the sculptures represents the Summa Sacra Via as he thought it ought to have been. One building is a triumphal arch, with a colossal figure under it, and an inscription on the cornice—ARCVS IN SACRA VIA SVMMA; another triumphal arch has the inscription ARCVS AD ISIS. Between these two is seen the Colosseum looking down upon it, represented as of two storeys only, and not quite the same as the existing building, but the figures under the arches are shewn as on the coin. Another sculpture on the same tomb represents the machine for raising large stones to the top of a high wall or building, described in Part III. of this work (Construction, p. 91). From the circumstance of this machine being represented upon the tomb, it seems most probable that the person here interred was the inventor, or had made some improvement in it, and that it was especially intended for the Colosseum, for which it certainly would have been very useful. The date of the tomb is of the first century[108]. Such a machine is mentioned by Vitruvius, and similar machines are still in use in some parts of Switzerland. The numerous walls that intersect the space under the stage shew clearly that there could be no area in this theatre, that there is no open space excepting on the stage itself, and this was the boarded floor, called the _arena_, from the sand with which it was covered. The latter is quite a different thing from an _area_, and yet almost all the modern writers on the antiquities of Rome fall into this mistake. The passage cited in a previous page from Dio Cassius, who describes what he saw, is quite decisive that the arena was a boarded floor covered with sand.