The first inauguration of the church of Hagia Sophia according to the Chronicon Paschale

Ἐπὶ τῆς αὐτῆς συνόδου τῶν ἐπισκόπων οὐ μετὰ πολλὰς ἡμέρας τοῦ ἐνθρονισθῆναι τὸν Εὐδόξιον ἐπίσκοπον Κωνσταντινουπόλεως τὰ ἐγκαίνια τῆς μεγάλης ἐκκλησίας τῆς αὐτῆς πόλεως ἐτελέσθη δι’ ἐτῶν λδʹ μικρῷ πρόσω ἀφ’ οὗ θεμελίους κατεβάλετο Κωνσταντῖνος νικητής, σεβαστός. ἐγένετο δὲ καὶ τὰ ἐγκαίνια αὐτῆς ἐπὶ τῶν προκειμένων ὑπάτων πρὸ ιςʹ καλανδῶν μαρτίων, ἥτις ἐστὶ μηνὸς περιτίου ιδʹ. εἰς τὰ ἐγκαίνια προσήγαγεν ὁ βασιλεὺς Κωνστάντιος Αὔγουστος ἀναθέματα πολλά, κειμήλια χρυσᾶ καὶ ἀργυρᾶ μεγάλα καὶ διάλιθα χρυσυφῆ ἁπλώματα τοῦ ἁγίου θυσιαστηρίου πολλά, ἔτι μὴν καὶ εἰς τὰς θύρας τῆς ἐκκλησίας ἀμφίθυρα χρυσᾶ διάφορα καὶ εἰς τοὺς πυλεῶνας τοὺς ἔξω χρυσυφῆ ποικίλα·

Chronicon Paschale, ed. L. Dindorf, 1 (CSHB, Bonn 1832), p. 544

The destruction of the Constantinian Hagia Sophia in 404

μετὰ δὲ τὸν ἄφατον καὶ δυσερμήνευτον ἐκεῖνον σκότον, φλὸξ ἀπὸ μέσου τοῦ θρόνου, ἐν ᾧ εἰώθει ὁ Ἰωάννης καθέζεσθαι,
καθάπερ ἐν μέσῳ σώματι κειμένη καρδία τοῖς λοιποῖς ἐξηγεῖσθαι μέλεσι τὰ τοῦ Κυρίου λόγια, φανεῖσα ἐπεζήτει τὸν ὑποφήτην τοῦ λόγου· ὃν οὐχ εὑροῦσα κατεβόσκετο τὴν σκευωρίαν. δενδρωθεῖσα δὲ εἰς ὕφος εἷρψεν διὰ τῶν ἁλύσεων ἐπὶ τὴν στέγην· ἔχεως δὲ δίκην τὴν γαστέρα φαγοῦσα, ἐπὶ νῶτον ἐφέρετο τῶν δωμάτων τῆς ἐκκλησίας, “μισθὸν τῆς ἀδικίας” ὥσπερ τὴν ἐπὶ ταύτῃ ὡρισμένην δίκην ἀποδιδόντος Θεοῦ εἰς σωφρονισμὸν καὶ νουθεσίαν τῶν οὐκ εἰδότων γε νουθετεῖσθαι <ἢ> διὰ τῆς ὄψεως τῶν τοιούτων θεηλάτων κακῶν·

P.R. Coleman-Norton, Palladii dialogus de vita S. Joanni Chrysostomi (Cambridge 1928), p. 62 [=Patrologia Graeca 47, col. 35-6]

The Justinianic Hagia Sophia after its second consecration in 562

Οὕτως ἀντολικὰς μὲν ἐπ’ ἄντυγας ὄμμα τανύσσας
θάμβος ἀειδίνητον ἐσόψεαι. ἀλλ’ ἐπὶ πάσαις
ἐκφύεται πολύκυκλον ὑπὲρ σκέπας οἷά τις ἄλλη..........(400)
ἁψὶς ἠερόφοιτος, ἀνευρύνουσα κεραίην
ἠέρι κολπωθεῖσαν, ἀίσσει δ’ ἄχρι καρήνου
ἄχρι βαθυκνήμοιο καὶ ἄντυγος, ἧς κατὰ νῶτον
πυθμένας ἐρρίζωσε μέσου κόρυς ἄμβροτος οἴκου.
ὣς ἡ μὲν βαθύκολπος ἀνέσσυται ἠέρι κόγχη,...................(405)
ὑψόθεν ἀντέλλουσα μία, τρισσοῖσι δὲ κόλποις
νέρθεν ἐπεμβεβαυῖα· διατμηγεῖσα δὲ νώτοις
πένταχα μοιρηθέντα δοχήϊα φωτὸς ἀνοίγει,
λεπταλέαις ὑάλοις κεκαλυμμένα, τῶν διὰ μέσσης
φαιδρὸν ἀπαστράπτουσα ῥοδόσφυρος ἔρχται ἠώς..........(410)

Paul Silentiarius, Descriptio Sanctae Sophiae in PG 86.2, col. 2135

The originality of the plan of Hagia Sophia

The design had no close antecedents. It is made up of elements that were current at the time, but these elements, as far as we kno, had not previously been put together in the same combination. Nor was St. Sophia imitated in the following centuries - that is, not until the Ottoman mosques of the sixteenth century. This uniqueness makes St. Sophia difficult to classify. It has been called a domed basilica because it has a longitudinal axis and rows of columns on either side of the nave, but such a designation does not sufficiently reflect the basic structural elements. According to another analysis, the design of St. Sophia was obtained by splitting Sts. Sergius and Bacchus in half and inserting the central dome between the two halves. It may make better sense to reverse this statement. For if we compare St. Sophia with the adjacent and contemporary church of St. Irene (abstracting, of course, the elements that were introduced into St. Irene in the eighth century), we can see that St. Irene has a better claim to being called a domed basilica, and that the singularity of St. Sophia lies precisely in the intercalation of the "two halves of Sts. Sergius and Bacchus."

C. Mango, Byzantine Architecture (London 1986), p. 61

The interior of Hagia Sophia

The design unfolds itself from the centre of the structure. Standing under the apex of the dome, the visitor begins to grasp the huge space. At first glance amorphus, it gradually falls into shapes and the shapes fall into place. From the vertical centre axis, space expands longitudinally into the huge niches to the east and west. It expands beyond, to the east into the forechoir and its apse, to the west into the entrance bay. From the niches, the space moves into the conchs that open diagonally on either side. It rises vertically into the main dome, gropes along its rim, sinks into the half-dome, widens and moves farther into the quarter spheres of the diagonal conchs. The sequence of spatial shapes develops both centrifugally around a middle axis and longitudinally from the entrance bay to the apse. The huge piers that support the arches of the main square and the subsidiary piers to the east and west are pushed aside into the aisles and galleries. In their place the eye encounters smooth, vertical planes; higher up rise the curvedsurfaces of arches, pendentives, domes and half-domes; and between the piers, two orders of arched colonnades open into aisles and galleries...
Clearly articulated by this rhythm of threes, fives and sevens, and clearly disposed, the spatial units are, nevertheless, not clearly delimited. All expand beyond what seem to be their natural borders. The eye wanders beyond the centre square into aisles and galleries whose shapes cannot be grasped. The gaze of the viewer is drawn beyond the curved arcades in the conchs and into the outer bays; yet the overlaping of these arcades with the windows in the outer walls precludes a ready understanding of the relationship between ancillary and main spaces. Within the inner shell, both the spatial volumes and their sequence are all intelligible. But beyond this core, space remains enigmatic to the beholder who is restricted to the nave. The form and interplay of spatial shapes is first established, then denied. Indeed, none of those spatial shapes are contained by the enveloping solids, be they piers, straight or vaulted surfaces. The term solids - in this architecture at least - is a misnomer. The piers are massive enough if seen from the aisles; but they are not meant to be seen. Their bulk is denied by their marble sheathing. The column shafts are huge, measuring two and a half to three feet in diameter, but the colourful marble counters the feeling of massiveness.

Krautheimer R., Early Christian and Byzantine Architecture (New Haven-London 1986, revised by R. Krautheimer and Sl. Ćurčić), p. 213-214.