From August 1978 to January 1979, an emergency excavation supervised by D. and P. Halbout (Rouen Archéologie) took place in the Haute-Vieille-Tour square in Rouen (Seine-Maritime, France), before the construction of an underground parking lot. The archaeological site is located near the Seine River and the centre of the ancient city of Rotomagus, main town of the Veliocasse people since the end of the last century B.C. Major discoveries occurred during the excavation: harbour facilities such as a dock built during the second half of the 1st century A.D. and large halls (warehouses?) replacing the wharf from the 2nd century on, next to an important domus in activity between the beginning of the 2nd century and the end of the 4th century. A hoard of 27 objects was found in the well of this aristocratic residence. It was dropped off half-depth during the filling of the structure as a consequence of the fire that hit the district at the beginning of the 3rd century. 25 objects made of copper alloy, including 23 pieces of a horse or chariot’s harness, a misidentified fragment of decoration and a large basin, were gathered here with a ceramic kettle and a deer skull. Most of these artefacts were concentrated in a wooden chest. They are currently stored in the Musée des Antiquités in Rouen. Despite this discovery being significant but odd, this set had never been properly studied before, only briefly presented in notes about the archaeological site. Therefore, the presentation of this assemblage is intended to be a contribution to the understanding of horse or chariot’s harnesses and hoarding in wells in the north half of Gaul during the High Empire. The identification and purpose of hoarding some of these items here, which remained unclear since then, can be specified or, at least, questioned in the light of studies and explorations recently conducted in wells on Roman sites. Thus, the combination of substantial metal mass (around 4.35 kg/9.59 lb) and an important number of objects is noteworthy enough for us to raise questions regarding the meaning and intention of its deposal. It was interpreted as a votive hoard at first, but the recent studies on hoarding in this kind of context favour a precautionary approach as for our potential hypothesis.