Intrigued by Maya civilisation from a very young age, 15-year-old Canadian William Gadoury thought he had made an incredible discovery from his study of ancient star charts. Through comparison, he found that the locations of the 117 known Maya cities correspond to the positions of the stars. Based on this, he believed he had spotted an unknown Maya city buried deep in the jungle. Although his theory has been dismissed by scholars, it shows how powerful the secrets of Ancient Maya civilisation are among people. <br> It isn't difficult to see why. Extending south from parts of what we now know as Mexico into Central America, Maya civilisation has been surrounded by mystery since its rediscovery in the 19th century. The Maya built impressive palaces and temples, including their representative step pyramids. What is most extraordinary about these complex structures is how they were built without the use of wheels, metal tools or even animal power. The Maya's understanding of mathematics and astronomy was also quite amazing. They applied this understanding to the Maya calendar, which was accurate to within 30 seconds per year. On top of all this was an achievement unique in the Americas at that time: a true writing system. It contained more than 800 characters with some signs representing animals, people and objects and others representing syllables. It was a writing system so complicated that, so far, no one has been able to interpret it completely. <br> The fact that Maya society was technologically primitive makes its achievements all the more incredible and mysterious. But the greatest mystery of all is what caused the Maya to abandon most of their great cities. By 700 AD, Maya civilisation was at its peak. Yet, within just a couple of generations, it began to mysteriously decline. The cities were left to be taken back by the jungle. When Europeans arrived in Central America in the early 16th century to claim its riches, the remaining Maya people were living in small settlements. <br> Why Maya civilisation collapsed remains a mystery. Was it a natural disaster? A deadly disease? Conflicts between cities? Or was it a combination of several different factors? Some research seems to indicate that Maya people themselves may have played a part in their downfall. They had turned wetlands into fields for growing grains, and had dug huge canal systems. As their population expanded, yet more land was needed for agriculture and more trees for construction. By changing the landscape in this way, it is possible that the Maya people unknowingly reduced their ability to deal with natural disasters. <br> Research also suggests that those natural disasters may have led to the decline of the Maya. Some recent studies have found that there were far fewer tropical cyclones than usual between 700 AD and 1000 AD. This is likely to have led to a series of droughts, each lasting for a couple of years, including a "megadrought" around 900 AD. Many scientists believe that these droughts were the main reason why Maya civilisation began to collapse at different rates in different places. These droughts would have led to food shortages, conflicts and, ultimately, the downfall of the cities. <br> Whatever the reasons, Maya civilisation largely disappeared within the deep jungle. Its once-great cities fell into ruin, leaving various mysteries for later people to solve. Meanwhile. the rise and fall of this civilisation must also leave us thinking about our own past, present and future. <br>