Tucked into a side alley in the old town, the Mensa Ponderaria is an unusual surviving fragment of Roman everyday life — a public office where merchants brought goods to be weighed against official standard measures. The original stone counter, with cavities cut to hold bronze standard weights, is still in place.
Visits are by request through the town's tourist office, but the inscription panel on the outside is readable from the street and gives a good sense of what survives. A reminder that Roman Tibur was a busy market town long before it became a retreat for emperors and cardinals.