The area of the Cryptoporticus occupies the central portion of the Domus Tiberiana and features a roughly square arrangement.
This originally underground structure probably belonged to a network of galleries and passages running through the foundations of the Domus and apparently connected to the perimeter area now visible (along the Clivius Victoriae to the north, below the Bastione Farnesiano to the west, etc.).
After being used as farming fields and as a place of spoliation of ancient materials throughout the Middle Ages and the Renaissance period, the area was eventually buried below the gardens of the Farnese family, which were built in the mid 16th century by cardinal Alessandro Farnese, who wished to ideally reconnect with the ancient Rome of the Caesars (VV. AA. “Palatino area sacra sud ovest e Domus Tiberiana”, Rome 1998 Maria Antonietta Tomei, “Scavi francesi sul Palatino, le indagini di Pietro Rosa per Napoleone III”, Rome 1999).
Regarding its construction, the whole vault is opus coementicium, but it was probably strengthened (or thoroughly reconstructed) back in Roman times with the erection of a 60cm-thick false wall rising up to the brick abutments (with an outer face made of horizontal joints and a conglomerate core of inert bricks) and finished on top with concrete conglomerate and tufa blocks.
This sheeting was probably required after some collapse, but its static function is actually null in the brick portion, as demonstrated by in-situ tests carried out with flat jacks (figures 1-3).
Some works were started in May 2006 to make a number of underground areas accessible again. The works were supervised by architect Giuseppe Morganti with the help of “Studio Croci e Associati” for the structural issues, of archeologist Ernesto Monaco for survey and constructional interpretation and, in the latest years, of archeologist Andrea Schiappelli for the excavations.
Generally speaking, structural damage consists in some deep cracks of the conglomerate vaulted roof crossing the barrel vault diagonally from the south-eastern corner along the springers, from one basement window to the next. This caused the blocks to slide for some centimeters along an oblique plan and resulted in the fall of large amounts of materials in proximity of one of the abutments (figures 4-7).
The concerned areas were eventually brought back to safe conditions with a number of works over the years.
Synthetically speaking, the works consisted in installing a number of supporting structures in the southern gallery, as necessary while entirely reversible interventions to guarantee safety. At the same time, the continuity of the masonry was rebuilt by means of injections into the cracks. (figure 8)
A most severe damage to the structure consisted in subsidence of some portions, caused by the collapse of the caves or galleries found below, which in some cases resulted in the collapse of about 80cm-thick layers between the cap and the springer. Along the north-south gallery, subsidence generated the collapse of the whole springers. (figures 9-12).
The cracks are found along the whole north-south longitudinal stretch of the gallery, although damage entities get progressively less severe southwards. Among various lesions, a horizontal crack is visible along the western wall of the vault, running along almost its whole length.
In the north-western corner area, it was understood that, at least for the western portion, the cause of damage lied in the collapse of a number of galleries and sewage plants. For the sake of safety, the collapsed areas were excavated and a number of underpinnings were erected with a view to rehabilitate the capacity of transferring load from the built structures to the ground.
[by Giorgio Croci e Alessandro Bozzetti]