"The latter is now empty, and the sixteen rows of fourteen columns each can be closely examined. It has been considered as exhibiting 'the highest development of the art of cistern building,' and thus 'in its particular sphere' resembling S. Sophia; 'like it the boldness of the construction was never again equalled by the Byzantines.'[67] The capitals are not as a rule highly ornamented, but some have monograms which are repeated in S. Sophia. Impressive though this great building is, it is not nearly so striking as the awful gloom of the Yeri Batan Serai (the Underground Palace)--the Basilike. There seems little doubt that this is the cistern alluded to by Procopius,[68] as made by Justinian under the Portico of the Basilica. 'It is still in perfect preservation, with the entire roof intact; its three hundred and thirty-six columns, twelve feet apart, arranged in twenty-eight symmetric rows, stand each in place, crowned by a finely wrought capital; it still serves its original purpose, supplying water from the aqueduct of Valens in as copious measure as of old.'[69] The capitals here are elaborately carved, in endless variety, and in the very finest style of the age. Darkness, immensity, and the colossal size of the columns seen in the flickering torchlight, make this one of the most impressive memorials of the sixth century. It is below ground what S. Sophia is above." They both belong, as Forchheimer and Strygowski have incontestably shown, to the age of Justinian. The capitals of the columns of the Bin Bir Derek are much plainer than those of the Yeri Batan Serai. Strygowski thinks that there the new impost capital was first used. "It is of the widest significance for the history of Byzantine art that here throughout the new 'impost capital' is employed in its plainest constructive form. It seems not improbable that the daring builder of the cistern was the first to make use of this form of capital, which completely broke with classical tradition, and is in such perfect accord with the exigencies of arch-architecture." But the analysis of the varieties of capital made by Lethaby and Swainson shows that the impost capital had probably been in use some years before the building of the Bin Bir Derek. The descent through a trap door and some worn steps from the stableyard of a Turkish house into the Yeri Batan Serai, lighted by a torch extemporised of sacking steeped in naptha, and wrapped round a pole, is an exciting experience. As you look out into the darkness you do not wonder that weird stories have grown up around its recesses, or that Gyllius who discovered it has a strange experience to record.[70]