Having now obtained all the dimensions of the building, except the 411 feet as the “totus circuitus” mentioned by Pliny, to which we shall come presently, the next point is to explain the architectural peculiarities of the structure. Unfortunately neither Pliny nor any other ancient author gives us the smallest hint as to how the interior of the building was arranged, and were it not for Guichard’s narrative we should have nothing but the analogy of other buildings to guide us. His account of the remains, and of the discovery of the chamber in the basement, is so clear, so circumstantial, and in every respect so probable, that there does not seem any reason to doubt that it was substantially correct, and no restoration can be accepted which does not admit of and explain its details. Although it is true no such catastrophe is expressly mentioned by any author, the position in which the horses of the quadriga were found renders it almost certain that the upper part of the building had been shaken down by an earthquake prior to the year 1402. Had the building been perfect, it is hardly probable that even such barbarians as the Knights of St. John would have knocked it down; but, be this as it may, in 1522 it seems that the basement was covered up by the _débris_ of the upper part and other rubbish, probably also by the sand and dust entangled in the heap. In consequence of this it was not till after a considerable quantity of the ruins had been removed that the Knights “saw an opening such as would lead into a cellar, and, taking a candle, let themselves down into the interior, where they found a beautiful large square hall, ornamented all round with columns of marble, with their bases, capitals, friezes, cornices, engraved and sculptured in half-relief. The space between the columns was lined with slabs and bands or fillets of marble of different colours, ornamented with mouldings and sculptures in harmony with the rest of the work, and inserted in the white ground of the wall, where battle-scenes were represented sculptured in half-relief.”[18]