S. Irene, now within the grounds of the Seraglio, is of more importance. It owes its original foundation to Constantine, but it suffered severely in the Nika riot and was rebuilt by Justinian in 532. It was again restored in 740. Little if anything has been done to it since the Turkish Conquest, and it may be taken as certain that its original structure remains practically unaltered. For the historical interest of its contents as well as for its architectural importance, it is well worth a visit; but it is rarely that permission is accorded to view it.[52] It has been used since the Turkish Conquest as an armoury, and an irardé from the Sultan himself is necessary to authorise the Minister of Ordnance to permit any one to see it. Its form is basilican, a nave with two aisles and an apse. The dome rests upon a drum lighted by twenty windows. It is probable that this was built by Justinian. In the apse is a characteristic feature which shows what must have been the arrangement at S. Sophia. There are five rows of seats for the clergy, facing west--an unusual number of seats I think, for at Ravenna there is but one row. Under the seats there is a passage round the apse. There were originally a narthex and an atrium. The narthex seems to have been thrown into the church, as is shown by the heavy pier supporting the gallery, with its counterpart in the outer walls ending abruptly at the wall plate. It seems probable that this was done in order to make room for the second dome, the original structure being that of the ordinary Roman basilica. The atrium seems to have undergone many changes: possibly it is entirely of Mohammedan work, as it has pointed arches. The interior of the church is solemn and impressive, an effect due to the great dignity of the general lines. Originally no doubt the walls and domes were covered with mosaics. Part of the apse still bears its decoration uncovered with the wash which is over all the rest of the surface. A gigantic cross of black tesseræ stretches up the vault, and large inscriptions remain over the arch. The apse is lighted by three great windows, a feature never seen in Roman basilicas till much later. The columns which support the galleries are plain, the arch resting on simple uncarved blocks. It may be seen, even from this brief description, how interesting the church is as a representation in Constantinople of the style brought to the East by the Christian architects of the Empire, and exposed to many foreign influences, but as yet showing no important signs of departure from the original type.