2002, 2004 and 2006 World Monuments Watch
The oldest surviving Byzantine monument in Istanbul, Küçük (“Little”) Hagia Sophia was constructed under the emperor Justinian near the southern city walls on the shores of the Sea of Marmara in a.d. 527–536. In 1504, the building was converted into a mosque. In the 1950s, the area in front of the city walls near the building was claimed from the sea and opened to traffic. A railway was later built next to the building. Although the sanctuary was restored in 1996, it was damaged by an earthquake in 1999, resulting in a series of cracks in the central dome that have allowed rainwater to seep in. This damage has been compounded by differential settlement, rising damp, and constant vibrations from the railway and road. Construction of a new sea wall nearby also raised the water table and affected the foundation of the mosque.