TERRACES AND SUBSTRUCTURES


One of the most effective and impressive ways concrete technology served the needs of Roman architects and engineers was the creation of massive terraced platforms to support large buildings or building groups, or even major cisterns, as the one serving the North African hilltown Tiddis (A80). This kind of site preparation could take the form of individual foundations or underpinnings for buildings, or retaining walls against the slope of a hill, or more elaborately, or a complex of interrelated vaulted chambers creating one or more building platforms or terraces.

Retaining walls, often built of solid, and intricately joined masonry, were fairly common in Greek and Hellenistic architecture. Often, they represented a logical structural solution for a hilly site. But, they could also create an exciting and dramatic architectural setting in themselves. The planning of the Hellenistic capital Pergamon in Asia Minor with its impressive acropolis top location was largely dependent on an artistic composition of multiple terraces. However, it was the Romans who realized the full structural advantages of building of massive substructures and exploited the functional and expressive potential of hilly sites. Roman terraces were not merely back-filled retaining walls, they often formed a structural armature of multiple vaulted spaces which could be used as shops, offices, or storage. The remains of these almost indestructable concrete substructure systems continue to impress us today even though the main architecture they supported, and dramatically presented, is often gone.

A number of Late Republican sanctuaries in Italy provide clear and well-preserved examples for terraced substructures. Travelers on Via Appia Antica, the coastal road from Rome, to the Sanctuary of Jupiter Anxur in Tarracina (Terracina) would have seen the massive terrace of the temple rising over the lofty headland for many miles (B20). The terrace, composed of a series of interconnected open barrel vault, is constructed entirely in concrete faced with opus incertum (B10, B9, B8). A simple stone molding at the springing of the arches provides the sole ornamental relief to the severe outlook of this structure, an early example of the kind of functional aesthetic destined for successful popular applications.


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(B7) In Praeneste (modern Palestrina), an entire hillside is built up in a series of terraces, ramps and stairs composing the Sanctuary of Fortuna Primigenia. The ancient shrine of Lady Luck was reorganized into an impressive ensemble in early second century B.C.(B19). The shape of the hill, carved as a total, integrated, architectural environment, mirrored the ritual act which started at the bottom of the hill, ascended and culminated, after many stops, in the theatrical area below the crowning tholos temple (B5, B4).


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At Tarracina a distinct and functional terrace platform provides the ground for the sanctuary above; here, the sanctuary is the series of formally and beautifully linked colonnaded terraces, ramps and exedras (B6). Behind the familiar classical elements is a sturdy core of concrete in massive retaining walls and rows of vaulted buttresses holding and molding the hill (B6, B3, B2, B1). Concrete, where visible, is faced in opus incertum and limestone quoins. This might have been covered in white stucco imitating marble veneer.


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(B40) The Palatine Hill, rising between the Forum Romanum and the valley of Circus Maximus in the heart of Rome, was an area favored by temples and aristocratic residences. The stately palace (the name "palace" is derived from the hill) the emperor Domitian and his architect Rabirius built on the eastern end of the Palatine, and known as Domus Flavia, or Domus Augustana (itself built of brick-faced concrete), necessicated an elaborate system of vaulted substructures (B38, B37, B36). Rabirius created his multi-leveled masterpiece in the last quarter of the first century A.D. In the following centuries the entire perimeter of the steep hillside was wrapped up in girdle of concrete. Today, the marble facades gone, the soaring barrel vaults of Palatine substructures are particularly impressive on the south, Circus Maximus side (B40, B39).


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Even on relatively flat ground large civic structures, such as temples and public baths, benefited from being raised on artificial terraces. This was clearly the case for Hadrian's Temple of Venus and Roma in Rome (B35, B34). Located at the east end of the Forum and overlooking the Colosseum, its vaulted substructures were used to store mechanical equipment for the great amphitheater. According to an anecdotal account, the aging architect Apollodorus (Trajan's architect) received imperial disfavor because he criticized Hadrian's design for making the terrace not sufficiently high and imposing. In Ephesus, Asia Minor, a double storied terrace shaped on the exterior by generously proportioned vaults (probably used as a shopping center to help the city's revenues), supported a massive temple dedicated to the Flavian family (B33, B32, B31, B30). Located on flat land near the sea, the colossal Antonine baths in Carthage (in modern Tunisia) were entirely lifted above the ground on a substructure of cross and barrel vaults carried by massive piers (B29, B28, B27). This basement city of massive structural forms was entirely functional because it contained extensive service areas necessary for a large bath.


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Unexplored and intriguing, perhaps, the most ambitious undertaking for shaping land for building was, surprisingly, not in Italy but in Asia Minor, in Nysa, a small Greco-Roman city in the Meander Valley. During the imperial period, the deep gorge for torrential waters which bisected the town was built from the ground up in a multi-level system of barrel vaulted structures (B26). The flat platform created united the divided city and supported an entire stadium nearly 200-meters long, and other large public buildings, plazas and streets, now visible only as fragments of collapsed mortared rubble masses. Glimpses of superimposed vaulted tunnels, and daring bridges, rising over the bottom of the gorge, visible among the lush vegetation, offer concrete witness to the Roman "knack" for technology and engineering in the service of architecture and urban design (B25, B24).


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