How do you track time? Do you have a calendar on your wall? How about a watch on your wrist? Do you know anyone who uses the calendar on their smartphone?

These are all common ways to measure time today. However, past civilizations didn't have the tools we use. They couldn't just glance at a watch or open the calendar on a smartphone. Instead, ancient peoples found other ways to measure time.

Like many ancient civilizations, the Mayas measured time by paying close attention to the sky. The Sun told them the time of day. The stars told them the season. The Mayas even noticed when the distance between Earth and Sun changed throughout the year.

Watching the sky is how the Mayas made their calendar. It was unlike most other ancient calendars. One difference was that the Mayan Calendar was round. That was because they believed time traveled in a circle instead of in a line. The Mayan Calendar also differed from other ancient calendars in the number of days it had. The Ancient Roman calendar had 304 days. The Chinese calendar has between 353 and 385. The Maya Calendar had 365 days per year, just like ours!

Do you have a calendar hanging up at home? The Mayan Calendar was too large and complicated to have in every house. However, the calendar influenced how the Mayas built their cities. Some Mayan buildings even helped them tell time! One example was in the Mayan city of Chichén Itzá.

Chichén Itzá was a large city from about 750 CE to 1200 CE. It was a center of trade and culture. Many structures in Chichén Itzá tell us about Maya culture. For example, a sinkhole in the city was full of jewels. Experts think the jewels were a sacrifice to a Maya god. Chichén Itzá also has the Americas' largest ball court. It's where Mayas played an ancient form of basketball! However, it's the city's largest building that is based on the Maya Calendar. Called El Castillo ("The Castle"), it sits in the center of the city, visible for miles around.

El Castillo's four sides face north, south, east, and west. Each side has 91 steps. The north side has one extra step leading to the flat top of the pyramid. Do the math - how many steps does El Castillo have?

That's right, 365! One step for each day in the Maya Calendar. El Castillo also matches the calendar in other ways. On the spring and autumn equinoxes, the sun makes special shadows on the sides of the temple. These shadows look like large serpents moving down the sides of El Castillo, continuing down the temple until sunset.

No one is certain what caused the fall of the Maya Empire. Sometime in the 13th Century, they left Chichén Itzá to the jungle. Explorers found the remains of Chichén Itzá centuries later in modern-day Mexico. Today, Chichén Itzá is well protected due to its status as one of the New Seven Wonders of the World. Tourists are not allowed to climb the steps of El Castillo. However, the city still has millions of visitors each year. What do you think happened to the Mayas? Would you like to visit Chichén Itzá? Maybe you could count the steps of El Castillo for yourself!