Luca Antognoli, 49, works for Roma Sotterranea, a group of urban speleologists commissioned by the city to explore Rome's subterranean spaces—an amazing array of temples, roads, houses, and aqueducts buried by history since the fall of the Roman Empire. According to tradition, the Cloaca Maxima ("great drain"), which runs beneath the Roman Forum, was built in the sixth century b.c., making it one of the city's oldest—if not the oldest—surviving structures. So it is surprising to learn, as Luca winds his way through the sludge-filled passage under Via Cavour, that the cloaca has never been fully explored and mapped.
In real life Luca Antognoli is a surgeon, and he has warned us to be careful not to expose our skin to the water, a potent mix of street runoff and raw sewage. Earnest and wide-eyed, he has taken the danger seriously, covering every inch of his body with gloves, boots, hooded wind suit, and mask—all hermetically sealed with duct tape. He motions sharply at a conduit disgorging a surge of ocher liquid into the cavern that aerosolizes into a mist, sending members of the group into a frenzy fitting masks over their faces.
He points out other conduits, some dumping clean water into the sewer from underground springs, some releasing dirty water. At one point, we pass through a sloping section down which brown sludge purls. Beyond this dangerous obstacle lies a deep hole where, sometime during the past 2,000 years, the floor has washed out, forcing everyone to inch along an unseen precipice in chest-high, scum-covered water. A joker in the group observes that it looks like schiuma, the cocoa-like foam on Italian espresso.
At a pile of rubble—bones, pottery sherds, and caked mud that nearly fill the entire space of the cloaca—the adventure comes to a halt. The sewer's barrel vault clearly reaches into the darkness beyond—one wonders how far.
Roma Sotterranea plans to send a remote-controlled robot to probe beyond the barrier; Luca expects to confirm that the great drain reaches the Baths of Diocletian, nearly a mile (1.6 kilometers) northeast. Who knows what treasures lie along the way, he says, noting that archaeologists had recently pulled a colossal head of Emperor Constantine from a sewer just like this, prompting speculation that the first Christian emperor may have been the victim of damnatio memoriae, as the practice of obliterating the memory of despised emperors was known in ancient Rome.