According to the ancient authors, Nero’s palace, built after the fire of AD 64, originally covered such a vast area – 80 hectares – as to be identified with much of the ancient city:
” … the Domus Aurea embraced the whole of Rome…“
(Pliny, Natural History, XXXII, 54)
and in another passage it is said that it
“… extended so far that it surrounded the city”
(Pliny, Natural History, XXXVI, 111)
Today, with the exception of some buildings and other isolated structures attributed to the complex during recent archaeological excavations and scattered between the Palatine and Caelian Hills, it is the “small” portion preserved on the Oppian Hill that gives us an idea of the size and lavishness of the emperor’s residence.
The pavilion, or more accurately what remains of this complex building, is subdivided into 150 rooms, and has a total length of about 250 metres and a width ranging from a minimum of 30 to a maximum of 60 metres.
To appreciate its exceptional size, suffice it to think that, including the galleries of Trajan, it has an area of about 16,000 square metres, the equivalent of around three football pitches. The fresco and stucco decorations on the walls and vaults are calculated to cover about 30,000 square metres, an area thirty times as large as the Sistine Chapel.
The palace presents such different characteristics in terms of both architectural development and the choice of decorative motifs on the walls and ceilings, that it can be clearly divided into a West Wing and an East Wing.
The architects Severus and Celer built the pavilion of the Domus Aurea in a dominant position on the southern slope of the Oppian Hill, oriented east-west and set into an artificial cut in the hillside; it was linked to the valley of the lake by a series of terraces. The southern façade, about 240 metres of which is currently documented, was preceded by a single-pitch Corinthian portico.
Sunlight flooded the rooms opening onto this southern front, but even inside the complex light penetrated into the rooms through peristyles and courtyards, as well as through windows opening into the walls and vaults.
This fundamental feature of the architectural project was definitively lost when Trajan turned the building into a vast underground container, filled with earth and rubble and reinforced with massive walls that cut through the larger rooms; it served as a foundation for the bath complex built on the summit of the hill.
Recent studies have definitively ascertained that the pavilion’s centre of symmetry was the Octagonal Room complex, and we can thus estimate a total façade length for the whole building of about 370 metres.
The West Wing
The West Wing was initially laid out according to a scheme very common in the Roman world, but that here became something new: though linked to the conception of the suburban villa, it also took on the landscape features typical of maritime villas, but on a far grander scale, and, for the first time, within the city itself. A series of rooms are arranged around a rectangular courtyard-garden, surrounded by an Ionic portico: on the south side in particular, a double row of rooms open alternately onto the courtyard or onto the valley with the lake, through another portico of the Corinthian order. Some scholars have interpreted these rooms, without much basis in fact, as the private apartments of the emperor.
The most representative rooms are placed on the axes of the courtyard: to the south is the Room of the Vault of the Owls (no. 29), perhaps a large triclinium, whilst to the east a vast hall (no. 44) originally opened via two colonnades onto the peristyle and towards a nymphaeum behind, decorated so as to create the illusion of a natural grotto (Nymphaeum of Ulysses and Polyphemus, no. 45). From the garden, lit by the sunlight, there were views through the shade of the porticoed hall over to the water jets of the nymphaeum fountain, to great scenic effect.
The East Wing
The East Wing has a far more complex layout, arranged around two polygonal courtyards at the sides of the Octagonal Room complex (no. 128).
The main rooms face onto the only fully preserved courtyard, with the Room of the Gilded Vault (no. 80) opening onto its centre, or are located along the southern façade overlooking the valley and again sheltered by the portico. On the northern side were service rooms and passageways; along the cut in the hillside a series of cryptoportici allowed for rapid communication between the different parts of the palace.
The focal point of the Neronian ground plan in this wing consists of the complex of the Octagonal Room – and its radial rooms – an extraordinary innovation in the history of Roman architecture for its spatial conception and bold construction.
The architect experimented with the resistance of concrete, adopting solutions never before attempted: the two cross-vaults characterizing two of the radial rooms seem to be the most ancient examples of this type of vault (nos 123 and 125). However, the architect focused his attention principally on the main room: over the octagonal structure is a pavilion vault which in proximity to the central aperture becomes a hemispherical dome.
The sense of lightness evoked by this architectural solution is further heightened by the fact that the vault, which appears to rest only on the broad jack arches leading into the radial rooms, can be seen from each of these through splayed windows and thus seems to float freely in space.
The two wings of the palace, so different in their layout, may have been built at different times, although the problem of the chronological sequence of the various wings has not yet been definitively clarified.
The pavilion also occupied part of the summit of the Oppian Hill with a second storey consisting of lightweight architecture, porticoes and gardens with ponds and fountains. These structures, investigated in the area above the Octagonal Room complex, were razed to just above floor level during Trajan’s building works.
As concerns the function of the palace, numerous features, such as the lack of doors, latrines, kitchens and heating systems, make it unlikely that this was a residential building: the emperor’s private apartments and the public rooms where he carried out his official tasks must have been located in that part of the Domus Aurea on the Palatine hill.
The pavilion on the Oppian Hill must have been dedicated to Nero’s private otium: inside, he and his guests could stroll and enjoy the space of the complex, the art works illuminated by the sun, the water gushing from the fountains and the splendid views over the park and the valley down to the waters of the artificial lake, stopping off in the main rooms dedicated to repose.
We know from the ancient sources that rich veneers of marble, gold and gemstones were frequently used in the rooms of the Domus Aurea and that some ceilings were covered in ivory. However, these precious materials were all removed and reused in the baths built by Trajan; it is still possible to read the decorative scheme of walls and floors by observing the imprints left on the mortar beds.
The most prestigious rooms, placed on the main axes of peristyles and courtyards, must have had walls clad in rectangular marble panels from quarries in Greece, Africa and Asia Minor, presenting marked variations in colour from white to yellow, red and green. These were framed by cornices and could be placed up to the impost of the vaults, which were covered with painted decorations – in large part preserved – sometimes enriched with stucco elements in relief.
The same type of decoration is also used on the external facade of the palace, a sizeable portion of which can still be seen in the so-called “Pentagonal Courtyard”.
Today the work of Fabullus, the paintings in the fresco technique that were not removed during Trajan’s building programme, still adorns the walls and vaults of countless rooms. These beautifully executed paintings are an exceptional legacy belonging to this vast and unique monumental complex.
The West Wing
Nero’s palace was first frequented in the Renaissance; by lowering themselves down from ground level, numerous artists managed to copy the subjects depicted on the vaults of many rooms that, still full of earth, looked like true grottoes. The books of copies circulated in Rome and, soon after, outside the city as well, leading to the dissemination of all those fantastic motifs known as “grotesques” which from then on were replicated in new paintings, sculptures and even on pottery.
Despite some differences with respect to what now survives, these antique drawings are of great help in reconstructing the original design of the painted decorations.
In this part of the palace, whose paintings are generically inspired by Greek mythology, the use of stucco is sparing and illusionistic architectural perspectives are rare; the characteristic feature of the paintings is the extremely fine detail of the decorative motifs, repeated in such a variety of combinations that they prevail over the figurative scenes.
The walls with a black, red or dark yellow background are generally subdivided by festoons, candelabra, plant tendrils or garlands into frames with small figurative panels at their centre; the surface of the vaults and lunettes, with a lace motif in a variety of colours, is reminiscent of the luxurious tapestries popular at the court of Alexandria, vividly described by ancient authors.
An unusual decoration is that of the Nymphaeum of Ulysses and Polyphemus (no. 45), where the surface of the vault presents imitation stalactites, made by mixing limestone concretions with cement, to suggest a natural environment, a grotto with water gushing out from its centre. Also unusual is the use of mosaics made from glass tesserae for the frieze and medallions inserted into the barrel vault; all that survives of these is the large octagonal medallion at the centre depicting the scene in which the wily hero, trapped in a cave, offers a cup of wine to the Cyclops to befuddle him and escape with his companions.
The East Wing
In this wing of the palace it is the Homeric poems, especially the Iliad, which inspired the choice of the subjects depicted on the painted panels of the main rooms, certainly the work of the painter Fabullus: at the centre of the vault of the Room of Achilles at Skyros, in a highly dynamic composition, the figure of the hero stands out among the daughters of the island’s king, Lycomedes.
In the Room of Hector and Andromache, one of the side panels immediately above the impost of the vault contains a fresco showing the warrior’s last farewell to his wife and little son before facing Achilles in the duel that was to lead to his death.
Overall, the decorative scheme consists of complex architectural features subdividing the walls and opening onto an illusionistic background with a wealth of fantastical and unreal motifs of eastern inspiration: human or animal figures are born from flower stems or end in plant tendrils. Everywhere, but especially in the large public halls, the paintings are enriched by numerous stucco elements in relief which underline the subdivisions of the vaults or give consistency to the figures depicted, or, alternatively, flesh out the façades of palaces and the other buildings shown in perspective.
The whole of this vast decorative fantasy repertoire is embellished with the abundant use of gold leaf, as in the Room of the Gilded Vault, copied and artistically reproduced in 1538 by Francisco de Hollanda in a watercolour now in the Escorial Library in Madrid.