by Dimana Trankova; photography by Anthony Georgieff

To enter the naos of the church, referred to as the Great Church by citizens of Constantinople when it was first built, visitors have to pass through the narthex and one of its nine arched doors. Most people choose to enter through the middle door, the largest, above which is a mosaic depicting Emperor Constantine the Great and Emperor Justinian offering the Virgin Mary and young Jesus small-scale models of Constantinople and the church. The stone floor on either side still carries the dents that mark the places where sentinels stood for some 1,000 years, guarding the gate through which only the sovereign could enter.

Justinian first passed through this entrance on 27 December 537 on the occasion of the consecration of the church, the construction of which had depleted the state treasury so much that new taxes had been levied. He was so stunned by the magnificence of what he saw that he exclaimed, "Oh Solomon, I have surpassed thee!" The Byzantine emperor did manage to surpass the king of the Jews. Despite earthquakes, invasions and a change in the gods it was devoted to, Hagia Sophia still stands by the Golden Horn, near the ruins of the Byzantine Hippodrome, the Blue Mosque and the Topkap? Palace of the Turkish sultans. It has been a museum since 1935 and is a must-see for all tourists coming to Istanbul.

Even 15 centuries on, anyone entering the building for the first time can still feel some of Justinian's excitement. Hagia Sophia is one of the few cases in which the superlatives of guidebooks pale in comparison with the true glory of the monument. Even Procopius of Caesarea, Justinian's court historian, who officially praised his master's constructions and military pursuits, but severely criticised them in his The Secret History, could not contain his admiration for the building, which was the largest church in the world in those times.

The light coming from the 40 windows of the 56 metre, or 184 ft high dome, with a diameter of 31 m, or 101 ft, gives the illusion that it is not standing on solid brick walls, but, to use Procopius's words, "covers the place beneath as though it were suspended from heaven by the fabled golden chain." The impression is so strong that even the restoration workers' scaffolding rising in the middle of the church can't spoil it.

How much longer this scaffolding will remain in Hagia Sophia is a question that no one can answer. At least, not before an important argument is settled: are they to restore the quotation from the The Light Verse (24:35) in the apex, inscribed by the famous calligrapher Mustafa Izzet Efendi in 1837-1839, or to remove (and destroy) it to reveal the Byzantine mosaic of Christ Pantocrator which lies under it.

The mosaics of Hagia Sophia were covered with plaster in 1453 when Sultan Mehmed II the Conqueror took Constantinople and converted the church into a mosque. The Swiss architect brothers Gaspar and Guiseppe Fossati are among the few people who have seen them since then. Sultan Abdul Mecit I hired the brothers to restore the building in 1847-1849, which allowed them to document the mosaics. A hundred years later, restoration is still largely based on the records they made when deciding which part of the Muslim compositions to remove in order to uncover the mosaics.

The Virgin with Child on the east apse, where the church altar used to stand, is one of these mosaics. Underneath it is the richly decorated mihrab, the niche pointing towards Mecca and the minbar, from where the muezzin preached. Turned into a museum by the reformer of the Turkish state, Kemal Ataturk, Hagia Sophia features the cultural heritage of two world empires. What remains from the Ottoman age is the sultan's pavilion; the oval medallions bearing the calligraphically inscribed names of Allah, the Prophet Mohammed and several caliphs; two marble ablution urns brought from Pergamum on orders of Murad III; several sultans' tombs; a washing fountain in the yard; and four minarets.