The people of Tiwanaku built a grand city several hundred years before their more famous Inca successors. High up on the barren Altiplano, its ruins are an atmospheric and fascinating complex of courtyards, pyramids, and masterful stonework. This civilization remains a mystery, however, with many key questions unanswered. Archaeologists are unsure what language they spoke or if they have living descendants today. It is not even clear how their society functioned and whether they expanded through imperial conquest or by peaceful cultural hegemony.Andean Civilization Before the TiwanakuCarved heads in one of the sunken courtyards, Franois Bianco, 2014. Source: Wikimedia CommonsBefore the conquistadors reached the Americas, indigenous civilizations developed across the Western hemisphere. They built cities in places as dispersed as the midwest of the present-day USA, Colombia, and (as archaeologists are increasingly realizing) even the Amazon rainforest. There were, however, two particular regions that gave birth to a succession of large cities and sprawling empiresMesoamerica and the Andes. Each has well-known civilizations associated with it: the Aztec and the Maya in Mesoamerica and the Inca in the Andes. Yet these, with the exception of the Maya, were relatively short-lived and only came after a succession of predecessors. Although both cultures built the biggest empires that their regions had ever seen, and they were interrupted when the Spanish reached the Americas, neither lasted much more than one hundred years.The earliest known evidence of humans quarrying to make tools in the Andean region dates back to 12,000 BCE. By 3500 BCE, people had begun to settle in sedentary communities and adopt agriculture at Sechin Bajo on the central coast of Peru. This lifestyle was taken up by numerous other peoples over the next 500 years, including those at a place named Jiska Iru Muqu. The transition away from a mobile existence of hunting and gathering is usually considered to be one of the first steps towards the development of complex civilization. Intriguing new evidence from another early Peruvian site, Caral-Supe, suggests that fishing can take the place of farming in this process. These first steps towards organized urban living created the foundations used by numerous civilizations to flourish over the following millennia.One of the glyphs that make up the Nazca Lines. Source: PBSAmong the most famous are the Nazca, who occupied the coastal deserts of southern Peru. It was this civilization that created the famous lines depicting animals and mythical beings that can only be properly viewed from the air. There were plenty of others, however, whose achievements were no less impressive. Beginning around 3500 BCE, and lasting almost 2,000 years, Caral-Supe may have incorporated as many as thirty different cities. This made their territory perhaps the most densely populated place on earth at the time.The Valdivia culture, who lived on the coast of what is today Ecuador, created a currency system based on the spondylous shells they pulled from the sea. This seems to have been adopted as far north as Mexico and as far south as Chile. Perhaps the largest of Tiwanakus predecessors were the Chimu. This empire was built on a highly stratified and bureaucratic form of social organization, allowing it to control 1,000 kilometers (600 miles) of Perus coastline.Who Were the Tiwanaku?The exterior wall of the Kalasasaya complex. Source: Wikimedia CommonsOne of the largest and longest-lasting cultures in the Andes was the Tiwanaku. Despite being one of the most important civilizations in the history of the Americas, relatively little is known about its people. It is clear that they controlled a vast region that stretched across parts of Peru, Bolivia, Chile, and Argentina. There is debate, however, as to whether it functioned purely as an empire or using a confederated model.Historians who endorse an empire structure believe that Tiwanakus people expanded and conquered their neighbors similarly to the Inca. On the other hand, the confederation model suggests that peoples made a deliberate decision to affiliate themselves with the Tiwanaku culture and adopt its customs, beliefs, and artistic style. If this were the case, these peoples would have retained much control of their own government and the freedom to disassociate themselves from the confederation. Either way, it is not known what language the people who inhabited the city spoke or if they have descendants today.The city was founded around 110 CE; however, it didnt see major growth or expansion until 600 CE. Around this time, many of its largest structures were built, and its distinctive cultural style developed. As well as incorporating other Andean peoples into its sphere of influence, a number of direct colonies were created in parts of Peru and Chile. These new settlements were formed by the Tiwanaku people themselves, rather than consisting of outsiders who had accepted their influence, but their purpose is unknown.The Ponce Monolith. Source: Wikimedia CommonsTheir culture drew on the shared Andean elements which defined its predecessors and contemporaries. Like those other civilizations, the Tiwanaku people created elements of their own as well. These included a distinct style of pottery and architecture as well as innovative farming methods. To combat the extreme conditions of the Altiplano, and to feed their growing population, the people of Tiwanaku built raised platforms on which to plant their crops. Between these they dug canals, which not only provided water in this arid landscape but helped combat frost. They also carved terraced fields out of hillsides to expand the area of suitable farmland available to them. This technique was famously reutilized by the Inca in places like Machu Picchu.Side-by-Side: The Tiwanaku and Wari CulturesA typical Tiwanaku style four-cornered hat. Source: The Metropolitan MuseumOne of the most intriguing features of the Tiwanaku civilization is their relationship with their Wari contemporaries. The Wari built their own great city, and between them, the two factions controlled almost the whole of the Andean region. Tiwanaku influence was concentrated in the highlandsmostly to the south, while the Wari focus was to the northwestalong the coast of Peru. There are remarkable similarities between the two states, including in their textile designs, suggesting some level of cultural exchange. There are enough differences in their buildings and artifacts, however, to be sure that they were separate cultures.Like the Tiwanaku, scholars dont know if the Wari built an empire by force or created a culture that others willingly embraced. Whichever is the case, they did so almost simultaneously to Tiwanaku, and the two civilizations seem to have come to an end at the same time as well. Being part of the same Andean world, their cultures shared some features, but the differences in their architecture and pottery allow scholars to distinguish them as separate entities. Without knowing whether they were expansive empires or not, it remains unclear whether they ever came into conflict.Both the Wari and the Tiwanaku civilizations seem to have collapsed around 1000 CE, having flourished for 400 yearsabout four times as long as the Inca empire. Their decline is no less mysterious than the rest of their history. It is unclear why both cultures started to disappear from the historical record but no new empire appeared which could have displaced them. The area surrounding Tiwanaku did suffer a severe drought around the time in question, and this was once thought to be the cause of their decline. Recent studies, however, suggest that this may have occurred soon after Tiwanakus collapse, ruling it out as a cause. There is evidence of destruction at the site, including burnt buildings and toppled statues. Whether these acts were carried out by unknown outsiders or by the population itself is unclear.The Tiwanaku RuinsTiwanakus Kalasasaya. Source: Wikimedia CommonsThe ruins of the Tiwanaku capital sit high on the Bolivian Altiplano, 3,850 meters (12,600 feet) above sea level. The land at this altitude is barren and empty, with yellow grasses being the only significant plant life. Visitors may find themselves struggling to breathe the oxygen-deficient air and shivering from the biting cold. Within sight of the complex is Lake Titicaca, the highest navigable lake on earth and one of both Bolivias and Perus most famous attractions. This location gives the site a dramatic feeling, and the hostile environment makes the fact that this great civilization developed here even more intriguing.The remains of the city are spread out over four square kilometers (2.5 miles), and at its height, it may have been home to as many as 20,000 people. Much of its expanse is unexcavated, and the site has suffered from looting over centuriesa sadly common occurrence to which even the most prestigious institutions are sometimes linked. This has meant that only the grandest buildings in Tiwanakus central core have been restored, and there are still many unanswered questions about its original layout. While some elements of the restoration work required the use of educated guesses, it is clear that the original builders wanted to make a statement through their monumental architecture.Much of the stone used to build Tiwanaku came from the shores of nearby Lake Titicaca. Source: CNNLike many American civilizations, the people of Tiwanaku liked to build pyramids. The largest in the complex is the Akapana Pyramid. Restoration work has not taken place, and unfortunately, much of its stone was taken away to be used in the construction of later buildings elsewhere. Visitors, however, can still view the remains, which take the form of a large mound that overshadows the rest of the site. It is aligned to the cardinal directions, and archaeologists believe that it consisted of six steps in the shape of an Andean cross. Its function is still a mystery, as are the purposes of many of its features. A sunken court was built on its summit alongside a basin for collecting rainwater. Inside the pyramid lies a network of channels, shafts, and weirs for controlling the flow of this water, allowing it to run into a moat that surrounds the structure.The majority of Tiwanakus monumental buildings take the form of raised platforms or sunken courtyards. The most imposing is the Kalasasayaa name which roughly translates to the standing stones. This two-tiered platform is 120 meters (390 feet) long and 120 wide, making it the structure that occupies the most space at the site. Before its retaining walls were reconstructed, only the vertical pillar stones were still standing, which is why Tiwanaku is sometimes referred to as the Stonehenge of the Americas. Today, the gaps between these columns have been filled in as they would have originally been, and the resulting walls showcase the advanced masonry techniques that the culture perfected. The Inca were also famous for their stonework, and although their methods were different, it seems likely that they drew some of their knowledge of the subject from this tradition.The Gateway of the Sun. Source: Berkeley ORIASAs with much of the site, Kalasasayas purpose is a mystery. Archaeologists think that the sunken courtyards that surround it were probably temples, but little more than that is known. Protruding from its walls are intriguing carved faces, each one unique. The identities of the people depicted by the monolithic statues dotted between them are also unclear. Their figures appear based on human forms but are decorated with animals such as fish, cats, and birds. Based on their alignment with surrounding mountain peaks, some scholars have argued that they represent the living spirits of those mountains.The most photogenic of Tiwanakus monuments are the two gateways dedicated to the moon and the sun. The Gateway of the Sun appears to be the more important of the two, being larger and decorated with more elaborate carvings. Standing in the center of the lintel is a figure that archaeologists have had no trouble identifyingwith his two staffs, the Andean creator god Viracocha is instantly recognizable. Among the most important of the regions deities, he was popular across many different civilizations, including the Inca. Here, he is surrounded by neat rows of anthropomorphic figures.The gateway was found cracked in half and partially collapsed, and so, like much of the site, it has been restored. This was done at the place where it was discovered, but there is disagreement about whether this is the position it occupied when the city was inhabited. The answer to this question has important ramifications for understanding the purpose of the gateways. Some believe that they formed physical parts of a calendar system and that their alignments with the sun and moon helped the people of Tiwanaku measure the passage of time.