The Maya lived in southern Mexico and Central America more than a thousand years ago. They were brilliant at maths, writing and watching the sky. Their pyramids were built so carefully that on certain days of the year, the sun makes a shadow that looks like a giant snake sliding down the steps.
Chichén Itzá is the most famous of them all. Its main pyramid, called El Castillo, has 365 steps - one for every day of the year. Each side has 91 steps, and 91 multiplied by 4, plus the top platform, is exactly 365. The whole pyramid is a giant calendar.
The Aztecs lived further north, around what is now Mexico City. Their capital, Tenochtitlán, was built on an island in the middle of a lake, joined to the land by long causeways. At its centre stood a tall double pyramid called the Templo Mayor. You can still visit its base in Mexico City today.
Pyramids weren't just decoration. They were used as observatories for watching the stars, as places to meet, and as huge solid markers visible from miles away. Building one by hand, with only stone tools, took thousands of people working together for many years.