The general style of the buildings at Hatra has been said to be “Roman or Byzantine;” and it has even been supposed that in the style of the ornaments and sculptured figures may be traced the corrupt taste and feeble outline of the artists of Constantinople. But there is abundant reason to believe that the Hatra Palace was built nearly two centuries before Constantinople came into existence; and, although the large-use of the round arch in vaulting may be due to the spread of Roman architectural ideas, yet there are no grounds for supposing that any but native artists, Parthian subjects, were employed in the work, or that it is other than a fair specimen of what was achieved by the Parthian builders during the later period of the empire. The palace of Volagases III. at Ctesiphon, which Avidius Cassius destroyed in his invasion, was most likely of the same general character--a combination of lofty halls suitable for ceremonies and audiences with small and dark sleeping or living rooms, opening out of them, the whole placed in the middle of a paved court, and the male apartments carefully divided from those of the women. The remains at Hatra are further remarkable for a considerable number of reservoirs and tombs. The open space between the town proper and the eastern wall and gate is dotted with edifices of a square shape, standing apart from one another, which are reasonably regarded as sepulchres. These are built in a solid way, of hewn stone, and consist either of one or two chambers. They vary in size from twenty feet square to forty, and are generally of about the same height. Some are perfectly plain, but the exteriors of others are ornamented with pilasters. The reservoirs occur in the paved court which surrounds the main building; they have narrow apertures, but expand below the aperture into the shape of a bell, and are carefully constructed of well-cut stones closely fitted together. The material used at Hatra is uniformly a brownish gray limestone; and the cutting is so clean and smooth that it is doubted whether the stones have needed any cement. If cement has been employed, at any rate it cannot now be seen, the stones everywhere appearing to touch one another. There are several buildings remaining in Persia, the date of which cannot be much later than that of the Hatra edifice; but, as it is on the whole more probable that they belong to the Sassanian than to the Parthian period, no account of them will be given here. It will be sufficient to observe that their architecture grows naturally out of that which was in use at Hatra, and that thus we are entitled to ascribe to Parthian times and to subjects of the Parthian Empire that impulse to Oriental architecture which awoke it to renewed life after a sleep of ages, and which in a short time produced such imposing results as the Takht-i-Khuzroo at Ctesiphon, the ruins of Shapur, and the triumphal arch at Takht-i-Bostan.