Hagia Sophia
Fatih, Istanbul, Turkey; Ayasofya Meydanı, Sultanahmet
Hagia Sophia is the clearest single starting point for understanding Istanbul’s layered past, because its fabric records the city’s Byzantine, Ottoman and modern eras in one building. Completed in 537 as the great church of Constantinople, it later became an imperial mosque, then a museum, and now functions again as Ayasofya-i Kebir Cami-i Şerifi. The building stands on Ayasofya Meydanı in Sultanahmet, inside Fatih on the historic peninsula, placing it at the centre of the city’s most concentrated cluster of major sights. Official material confirms that it remains both a place of worship and a monument open to visitors, with designated visitor routes and the worship area managed separately from touring areas. That dual role matters for trip planning. Entry to the mosque itself is free, but visitor circulation is shaped by prayer times and on-site controls, so this is not a simple walk-in museum visit. The current official guidance stresses that some mosaics in the worship area are screened during prayers, while broader conservation measures are intended to protect the monument as a shared world heritage site. As an editorial number one, Hagia Sophia earns its place through historic weight, central siting and the fact that it frames any wider day in Sultanahmet better than any other single stop in Istanbul.