Taken to nine other planes

Nicholas Saunders is transported by the 'otherness' of Aztec culture

The Aztecs were the great conquest culture of Mexico. Between 1519 and 1521, Spanish conquistadors under Hernán Cortes fought, subdued and finally destroyed Mesoamerica's last major pre-Columbian civilisation. The extended conquest, and its long drawn-out proselytising aftermath, has provided a rich if uneven record of the Aztec achievement. The cross-cutting evidence of history, archaeology and anthropology has provided a rich tapestry of knowledge. We know more about the Aztecs than any other ancient American culture, and are tempted to view the pre-Aztec past through the lens of this remarkable civilisation.

Aztecs is the catalogue of the hugely successful exhibition at the Royal Academy. It is one of those rare publications - a lavishly illustrated book full of scholarly yet accessible insights. With objects drawn from the world's museums, the exhibition and this book represent the most impressive array of Aztec material culture ever assembled.

The painstaking attention to detail and planning that is such a feature of the exhibition and its associated events is clear in the organisation of the book. It is divided into three parts. The first part is a series of nine short thematic essays dealing with topics such as Aztec society, art, religion and discovery and excavation of the Great Temple in Mexico City in the late 1970s. The second part has 11 photographic essays that explore the human form, the natural world, the gods of life and death, gold and Indo-Christian art. Finally there is a treasure trove of 396 catalogue entries describing the history and significance of each item.

One of the most difficult problems in understanding Aztec culture and the objects that it created is to enter the mind of a society so dramatically "other". Alfredo López Austin's account of Aztec natural and moral philosophy leads us authoritatively through this entwined world of myth, calendrics and multifaceted gods. Here we find a cosmos divided into nine celestial planes, nine planes of the underworld and the earthly realm in the centre, through which ran the great celestial tree as axis mundi .

A mythic charter for the infamous Aztec practice of human sacrifice is found in the cosmogonic "myth of the five suns". Here, the proto-sun became supreme among his fellow deities by an act of self-sacrifice, but refused to start his cosmic journey until they too accepted such a fate. These acts created a debt that humans were expected to repay through their own sacrifices, thereby recapitulating the myth of cosmic origin and keeping at bay the cataclysm of world destruction. Sacrifice, therefore, was less about death than the renewal of life - a still widely overlooked corrective to the common acceptance that these are savage acts of bloodlust. Analogy was a central mechanism in this intricately fashioned ritual world. To avoid damaging the sun during eclipses, human sacrifices were restricted to albinos as being people already full of brilliance. Every 52 years, the world's light was rejuvenated by the sparking of a new flame in the chest of a victim with the aid of a fire-drill, and gods themselves had their energies recharged through the ritual killing of specially chosen human impersonators. The sophistication of analogical reasoning that characterised Aztec notions of sacrifice were but part of a wider structuring of the natural world and of the place and role of humans within it.

Aztec warfare illustrates this in an insightful way. Waged often to gain sacrificial victims for the gods, the Aztec elite's warrior societies of the jaguar and eagle were at the forefront of military engagements. These men were symbolic predators who dressed as jaguars and eagles, and engaged in the sacrifice of prisoners as well as in combat. In typically Aztec (and Mesoamerican) fashion, they partook of the predatory nature of their carnivorous totems in a mythic association between humans and animals. For the Aztecs, the natural world was a source of metaphor, natural prototypes becoming cultural paragons. While this way of looking at the world was pan-Amerindian, its Aztec expression was enshrined in the material culture of art to an unprecedented degree.

For the Aztecs, the world of animals and plants was a fertile mix of folklore, myths and acute observation. While a person may have been endowed with the qualities ascribed to an animal by virtue of being born under its calendrical sign, natural forms were also respected. In López Austin's photographic essay on "The natural world" are beautifully rendered stone sculptures of lizards, fish, snakes, pumpkins, eagles and dogs. A cornelian grasshopper and a greenstone insect reveal a fascination with detail born of close first-hand study. The mythic attributes and supernatural powers ascribed to animals were no mere substitutes for empirical zoological understanding - rather, they complemented it, structuring physical reality according to Aztec beliefs.

Arguably the most impenetrable and fascinating aspect of Aztec life was the pantheon of gods, whose ambivalence and supernatural powers seemed to the Spanish to control every aspect of life and death. The multiplicity of gods may more accurately be seen as innumerable guises adopted by a much smaller number of recognisable deities. These supernaturals were associated symbolically with animals, and appeared to take human form - though many sculptures may in fact be human impersonators dressed in the deity's ritual attire. Their names are as evocative as their natures, such as Xipe Totec (Our Lord the Flayed One), Huitzilopochtli (Left-sided Hummingbird), Quetzalcoatl (The Feathered Serpent), and the supreme deity Tezcatlipoca (Lord of the Smoking Mirror).

Each god had ritual associations with colour and directions, and all possessed their own calendrical duties. Each had a distinctive appearance, costume and paraphernalia: Xipe Totec was represented as wearing the skin of a sacrificial victim, Xochipilli (the god of springtime renewal) was decorated with flowers, and Tezcatlipoca wielded his magical obsidian mirror. Many of these gods were associated with one or more aspects of fertility through sacrifice - hence their often-gruesome appearance to western eyes.

One reason we know so much about Aztec religion compared with that of their predecessors is that we have a precious few of their painted books, known as codices. Supplementing the startling and sometimes still-painted sculptures, the evidence from these native pictorial documents is explored by Miguel León-Portilla. He stresses that there are several kinds of codex - those truly pre-conquest, and others post 1519-21, which, while painted by indigenous scribes, nevertheless have Spanish commentaries appended.

Whether any of the pre-Columbian codices are Aztec is still debated, but other post-conquest examples do relate to Aztec culture. Still others are pre-Columbian but not purely Aztec, though clearly belong to closely associated societies.

One of the most interesting and dazzling of these books is the Codex Borbonicus, which deals with Aztec spirituality. Dating probably from the first decades of the Spanish era, it colourfully depicts the 260-day ritual "Book of Days", which relates the fates associated with each day. Another, the Codex Fejérváry-Mayer, has a now-famous image of the Aztec world, showing the five cosmic directions - east, north, south, west, and centre.

More explicitly Spanish is the Florentine Codex, which tells of beliefs, gods, and retrospective omens of the Spanish arrival as collected by the Spanish priest Bernardino de Sahagún. These pictographic codices, together with the glyphic writing of the classic Maya, mark out Mesoamerican civilisation as a literate phenomenon - unlike the great civilisations of South America, including the Incas.

The 1978 discovery of the Great Temple in Mexico City transformed our knowledge of Aztec civilisation. Until then, Aztec archaeology had been patchy, and most understanding came from the codices and Spanish accounts of the conquest. In his thematic and photographic essays, Eduardo Matos Moctezuma, the excavator of the Great Temple, describes the discoveries and their significance.

Astonishing finds were made, often as sacred offerings buried in different locations within the temple complex. Feline skeletons with jade balls grasped in their fangs, a giant terracotta model of an eagle warrior, carved stone sculptures of seated and reclining gods, and bright votive fired clay vessels of Tlaloc the rain deity, and the maize goddesses Xilonen and Chicomecoatl. Stunning sculptures of snake heads and eagles, delicately worked and polished obsidian ritual ornaments and curious flint knives decorated with eyes and teeth all emerged from the site. After 20 years of study, these artefacts have yielded surprising insights. The presence of greenstone masks from the Olmec culture (c. 1100-600BC) and the Teotihuacan culture (c. AD300-600) suggests the Aztecs collected their own past.

Excavations revealed a sequence of Great Temples, one built on top of the other, and evidence that while the building was one temple-pyramid, two separate temples crowned its summit. One was associated with the Aztec tribal war god Huitzilopochtli, the other with Tlaloc. As the actual and symbolic centre of the universe, the Great Temple was the Aztecs' most holy place, shaped as two sacred mountains where bloody sacrificial rites restated and re-enacted the primordial accord with the gods of creation - human life for the continuation of the world.

The Spanish conquest and aftermath is an oft-misunderstood chapter in the history of Aztec culture. Yet the symbolic complexities of Indo-Christian art as described by Eleanor Wake open our eyes to the imaginative ways in which indigenous Mexican peoples accommodated the new Christian order to their ancient beliefs and art styles. Age-old Mesoamerican concepts are represented in an explosion of syncretic art objects.

On carved stone crosses, Christ becomes the tree of life, spilling his fertilising blood on to the sacred earth in the same way as the Aztecs and their predecessors had done. His wounds were represented by concentric circles, the Aztec sign for chalchihuitl - the precious liquid that can be both water and blood. Equally stunning is the early 16th-century featherwork mosaic of Christ the Saviour, made more valuable by the rapid demise of the Mexican feather worker's art. More enigmatic is the slab of obsidian in its painted and gilded colonial wooden frame. Obsidian was a magical as well as practical material in the Aztec world, and was used to make divinatory mirrors. Here it is described as either a mirror or a portable Christian altar - the latter an ironic possibility given obsidian's native identification with the Aztec deity Tezcatlipoca, whom the Spanish regarded as Satan incarnate.

Aztecs is a unique record of a magnificent exhibition. It is also a dazzling visual testament to the rich and complex achievements of pre-Columbian America's most famous civilisation.

Nicholas J. Saunders is lecturer in material culture, University College London.