You emerge into an illuminated space: golden paint, golden mosaics, golden inscriptions.
Some of the mosaics remained hidden from the 15th century to the 20th (Mehmet wasn't so visionary that he would keep Christian icons on view).
Ayasofya is a reminder that nothing - not even a monumental building - stays the same. We change and adapt and so do our holy places (and isn't there something fascinating about the journey from Christian sacred space to Muslim sacred space to museum - the modern world's oxymoronic version of a secular/sacred space?) It's also a reminder that, with vision, these changes can - paradoxically - help to safeguard our holy places.