Ephesus remained the most important city of the Byzantine Empire (after Constantinople) in the 5th and 6th centuries. The emperor Constantine rebuilt much of the city and erected a new public bath. In 406 John Chrysostom,
The town was again partially destroyed by an earthquake in 614.
The importance of the city as a commercial centre declined as the harbor slowly filled with silt from the river (today, Kucuk Menderes) despite repeated dredges during the city's history (today, the harbor is 5 miles inland). The loss of its harbor caused Ephesus to lose its access to the Aegean Sea, which was important for trade. People started leaving the lowland of the city for the surrounding hills. The ruins of the temples were used as building blocks for new homes. Marble sculptures were ground to powder to make lime for plaster.
Sackings by the Arabs first in the year 654-655 by caliph Muawiyah I, and later in 700 and 716 even hastened the decline.
When the Seljuk Turks conquered it in 1071-1100, it was a small village. The Byzantines resumed control in 1100 
and changed the name of the town into Hagios Theologos. They kept control of the region until 1308. Crusaders, passing through, were surprised that there was only a small village, called Ayasalouk, where they had expected a bustling city with a large seaport. Even the Temple of Artemis was completely forgotten by the local population.
Turkish era
The town was conquered in 1304 by Sasa Bey, an army commander of the Mentesogullari principality. Shortly afterwards, it was ceded to the Aydinogullari principality that stationed a powerful navy in the harbour of Ayaslug (the present-day Selcuk, next to Ephesus). Ayasoluk became an important harbour, from where the navy organised raids to the surrounding regions.
The town knew again a short period of flourishing during the 14th century under these new Seljuk rulers. They added important architectural works such as the Isa Bey Mosque, caravansaries and Turkish bathhouses (hamam).
They were incorporated as vassals into the Ottoman Empire for the first time in 1390. The Central Asian warlord Tamerlane defeated the Ottomans in Anatolia in 1402 and the Ottoman sultan Bayezid I died in captivity. The region was restored to the Anatolian Turkish Beyliks. After a period of unrest, the region was again incorporated into the Ottoman Empire by sultan Mehmed II in 1425.
Ephesus was eventually completely abandoned in the 15th century and lost her former glory. Nearby Ayaslug was renamed Selcuk in 1914.
