It is not quite clear whether the hole the Knights found was in the roof of the apartment or in its side, at some height above the floor. I strongly suspect the latter, but of this more hereafter. From the description it is quite clear that this hall was not the cella surrounded by the pteron as described by Pliny; for on any theory of restoration the floor of that must have been 50 feet from the ground, and it could consequently neither have been buried nor could the Knights have descended into it. It must have been in the basement, and if so must have been lighted. For it need hardly be stated that the Greeks would never have applied such an amount of ornamentation to a hall where it could not have been perfectly seen.[19] It could not have been lighted by windows in the ordinary sense of the term, as its walls could not be less than 21 feet thick, but there seems no difficulty in introducing any amount of light required by the mode suggested in the accompanying plan and sections.[20] As shown there, there are four openings on each side, 17 feet high by about 6-1/2 wide, opening into a corridor 8 ft. 6 in. in width, which was separated from the outer air by piers 4 feet in width. It was, in fact, a _peristele_ under a _peristyle_. As these words exactly express the difference between the two corridors, they will be so used in future—peristele (from περι and στήλη, a stele) being used for the lower, and peristyle (from στυλος, a column) for the colonnade which it supported. If more light was wanted, it could be introduced to any desired extent at the end opposite the door, but the eight openings shown in the plan are, it is conceived, more than sufficient. By this arrangement, too, the light is introduced in the most pleasing manner. The direct rays of the sun could never penetrate the sepulchral chamber, but a diffused high light was introduced sufficient to show all its beauties without disturbing its repose. The existence of some such arrangement as this appears indispensable in order to understand the passage in Martial:— “Aere nec vacuo pendentia Mausolea Laudibus immodicis Cares ad astra ferant.” It is absurd to suggest that this might refer to some little structural difficulties about a roof, as no roof was ever less seen than that of this building. Besides, a roof is not a mausoleum; but the upper chamber here was so called, according to Pliny; and the fact, therefore, of people being able to walk round the building and see the town on one side, or the shipping and the sea on the other, through it, _under its floor_, may well have led the Halicarnassians to boast that their great tomb was supported in the air. This would in those days be even more striking than at present, inasmuch as there was not, so far as we now know, a single two-storied temple or tomb of any importance then existing.