Archeological evidence suggests they lived in small villages, composed of six to 12 houses in the very fertile lands between the rivers, and lived by agriculture and cattle-raising. Finds of horse skeletons in graves suggest a strong equestrian preoccupation. On the south bank of the Waal (in what is now Nijmegen) a Roman administrative center was built, called "Oppidum Batavorum". An Oppidum was a fortified warehouse, where a tribe's treasures were stored and guarded. This centre was razed during the Batavian Revolt. The Smetius Collection was instrumental in settling the debate about the exact location of the Batavians.