'Groma' weight in the shape of amphora with suspension loop. Roman period, 1st-3rd century AD. 46x19 mm. 43.40 g. In the building of a Castra, after having flattened the ground and before starting the ditch and wall construction, an agrimensor (land surveyor) drew the locations of the streets and of the wall, beginning from the center of the field, using the groma. It follows the description of this topographical tool and its use. (https://legioneromana.altervista.org/content/how-use-roman-groma?language=en).