The ancient Maya, a diverse group of indigenous people who lived in parts of present-day Mexico, Belize, Guatemala, El Salvador and Honduras, had one of the most sophisticated and complex civilizations in the Western Hemisphere. Between about 300 and 900 A.D., the Maya were responsible for a number of remarkable scientific achievements–in astronomy, agriculture, engineering and communications.

The Ancient Maya

Mayan civilization lasted for more than 2,000 years, but the period from about 300 A.D. to 900 A.D., known as the Classic Period, was its heyday. During that time, the Maya developed a complex understanding of astronomy. They also figured out how to grow corn, beans, squash and cassava in sometimes-inhospitable places; how to build elaborate cities without modern machinery; how to communicate with one another using one of the world’s first written languages; and how to measure time using not one but two complicated calendar systems.

Did you know? The written language of the Maya was made up of about 800 glyphs, or symbols. Each one represented a word or a syllable, and could be combined with the others in an almost infinite number of ways. As a result, there were three or four different ways to write almost every word in the Mayan language.

READ MORE: Why the Maya Abandoned Their Cities

Mayan Astronomy and Calendar-Making

The Maya strongly believed in the influence of the cosmos on daily life. Consequently, Mayan knowledge and understanding of celestial bodies was advanced for their time: For example, they knew how to predict solar eclipses. They also used astrological cycles to aid in planting and harvesting and developed two calendars that are as precise as those we use today.

The first, known as the Calendar Round, was based on two overlapping annual cycles: a 260-day sacred year and a 365-day secular year. Under this system, each day was assigned four pieces of identifying information: a day number and day name in the sacred calendar and a day number and month name in the secular calendar. Every 52 years counted as a single interval, or Calendar Round. After each interval the calendar would reset itself like a clock.

Because the Calendar Round measured time in an endless loop, it was a poor way to fix events in an absolute chronology or in relationship to one another over a long period. For this job, a priest working in about 236 BC devised another system: a calendar that he called the Long Count. The Long Count system identified each day by counting forward from a fixed date in the distant past. (In the early 20th century, scholars found that this “base date” was August 11 or August 13, 3114 BC.) It grouped days into sets, or cycles, as follows: baktun (144,000 days), k’atun (7,200 days), tun (360 days), uinal or winal (20 days) and kin (one day).

The Long Count calendar worked the same way that the Calendar Round did–it cycled through one interval after another–but its interval, known as a “Grand Cycle,” was much longer. One Grand Cycle was equal to 13 baktuns, or about 5,139 solar years.

Pyramid at Chichén Itzá

The Maya incorporated their advanced understanding of astronomy into their temples and other religious structures. The pyramid at Chichén Itzá in Mexico, for example, is situated according to the sun’s location during the spring and fall equinoxes. At sunset on these two days, the pyramid casts a shadow on itself that aligns with a carving of the head of the Mayan serpent god. The shadow forms the serpent’s body; as the sun sets, the serpent appears to slither down into the Earth.

READ MORE: Mayans: Civilization, Culture & Empire

Mayan Technology

Remarkably, the ancient Maya managed to build elaborate temples and great cities without what we would consider to be essential tools: metal and the wheel. However, they did use a number of other “modern” innovations and tools, especially in the decorative arts. For example, they built complicated looms for weaving cloth and devised a rainbow of glittery paints made from mica, a mineral that still has technological uses today.

Until recently, people believed that vulcanization–combining rubber with other materials to make it more durable–was discovered by the American (from Connecticut) Charles Goodyear in the 19th century. However, historians now think that the Maya were producing rubber products about 3,000 years before Goodyear received his patent in 1843.

How did they do it? Researchers believe that the Maya discovered this process accidentally, during a religious ritual in which they combined the rubber tree and the morning-glory plant. Once they realized how strong and versatile this new material was, the Maya began to use it in a variety of ways: to make water-resistant cloth, glue, bindings for books, figurines and the large rubber balls used in the ritual game known as pokatok.

The Decline of the Maya

Despite the Maya’s remarkable scientific achievements, their culture began to decline toward the beginning of the 11th century. The cause and scope of the decline is a matter of some debate today. Some believe that the Maya were wiped out by war, while others attribute their demise to the disruption of their trade routes. Still others believe that the Maya’s agricultural practices and dynamic growth resulted in climate change and deforestation. While much of what was left of the ancient Maya culture was subsumed by the Spanish conquistadors in the 16th century, the legacy of Mayan scientific achievement lives on in the discoveries that archeologists continue to make about this amazing ancient culture.

WATCH: Full episodes of The UnXplained online now.