The river is also valued by archaeologists owing to the large number of artifacts, dating as far back as the Neolithic, discovered here. The outlet of the Ulla River and the mouth of the estuary, called Ría de Arousa, are the two sites where archaeologists have discovered remains consistently. Rock carvings have been discovered here. The Ulla River is also important because it is the river in the northwest of the Iberian Peninsula to produce a large number of watery hoards, which were discovered in its lower reaches and its mouth.
The Ulla river basin is marked in deep blue in this map of the Galician river basins
According to E. Bascuas, "Ulla" is a form belonging to the old European hydronymy, and derived from the Indoeuropean root *wel- 'wheel, rotate'. This toponym is registred in 906 as "(fluvius) Volia", which had derived from a previous form *Wulia.