Complex sentence: In Aalen and Wasseralfingen, gold and silver coins left by the Celts were found, who also fortified the Schloßbaufeld settlement with sectional embankments and a stone wall.
Split into simpler sentences: In Aalen and Wasseralfingen, gold and silver coins left by the Celts were found. The Celts were responsible for the fortifications in the Schloßbaufeld settlement consisting of sectional embankments and a stone wall.