Complex sentence: The Devil's Dykes were a late Roman line of fortifications built along the western bank of the Tisia river (modern "Tisza") during the reign of Constantine I (312-327).
Split into simpler sentences: The Devil's Dykes were a late Roman line of fortifications built along the western bank of the Tisia river (modern "Tisza"). They were constructed during the reign of Constantine I (312-327).