Forma Urbis Romae: The Severan Marble Plan Is Tantalizing Jigsaw Puzzle From Hell

The Forma Urbis Romae, or Severan Marble Plan, was an immense 3rd century map of the city of ancient Rome, carved into 150 adjoining slabs of marble and covering a wall rising over four stories tall. It was created at an approximate scale of 1:240 and measured 60’ wide by 45’ high. The map depicted the location of the buildings and structures that existed in central Rome, and it was detailed enough to show the floor plans of nearly every temple, bath, house, shop, warehouse, and apartment building in the city’s core. Unfortunately, only fragments of the map still survive, but they provide details about the topography and lesser-known neighborhoods of ancient Rome that otherwise would have been unknown today.

The map was created sometime between 203 and 211 A.D, during the time of the emperor Septimius Severus. It may have been used by the city prefect (praefectus urbis) or, perhaps was merely a decoration for his office, which stored more practical sized maps drawn on papyrus. The marble map was affixed to an interior wall of what was then the Temple of Peace (Templum Pacis). The same wall is now an exterior wall of the 6^th century Church of Saints Cosmas and Damian (Basilica of Santi Cosma e Damiano). The holes in the wall where the bronze clamps attached the marble slabs in place can still be seen.

The Severan Plan was gradually destroyed during the Middle Ages, as the marble stones were torn away to be used as building materials or for making lime for fertilizer or cement. Whatever was left fell to the ground, breaking apart into many unrecognizable pieces and becoming buried over time.

In the 16^th century fragments of it were found, but they did not elicit much lasting interest. In later years, as more fragments were found (or lost and then rediscovered) there was an interest in trying to fit the pieces together. The work was like a giant jigsaw puzzle, with only a few famous landmarks, like the Colosseum, incised into the stone to give any clue as to how the pieces should be assembled.

To date, only about 10% to 15% of the original surface area of the plan is known to still exist, and that much is broken into almost 1200 pieces of various sizes. Some of these fragments are relatively easy to piece together, but others are more difficult since their adjoining pieces don’t exist, or because the fragments have been altered (such as when their edges were sawn off in the 18^th century to fit within display frames in a museum). In modern times, archaeologists have turned to using computer and coded algorithms to try to determine the correct placement of the pieces.

Additional fragments continue to be discovered in Rome, and there may be more so in the near future. Excavations for Rome’s new Line C metro subway are being done at the site of the Forum of Peace, where the plan was located. Great care is being taken to preserve any antiquities that may be found, and it is hoped that among the artifacts they find will be more pieces of the plan. Since some of the map fell from the wall to the ground through the years as it was torn away or dropped, it is possible that more fragments may yet be unearthed from this important archaeological site.

The piecing together of the world’s greatest jigsaw puzzle continues.