The visible remains are essentially the city of the first to fourth centuries A.D., when it flourished as an important Christian center. The reason the structures have been so well preserved is, ironically, because of its rapid decline and virtual abandonment shortly thereafter. The progressive silting up of the Kayster River choked the once-bustling harbor of Ephesus beyond the point where dredging operations could maintain its contact with the sea. A growing marsh buried the precinct of Artemis and isolated the city’s buildings. The dwindling populace relocated on higher ground to the north, in the area of the present-day town of Seljuk.