stone porphyry paving made with porphyry stone blocks of irregular , called opus incertum, in a pedestrian zone

irregular shape pattern porfido porphyry outdoors pebble pavement paving cobblestones cobble cobblestone stone material floor flooring walkway traditional sidewalk paved natural block pedestrian zone footpath patio tradition pave building activity old the past historical split splitted opus incertum construction industry stones limestone pathway footway masonry