Hundreds of years ago, a towering temple stood at the center of what is now Mexico City. This Great Temple was a symbol of the power of the Aztec Empire—an empire that stretched across much of Mexico.

Would you put on your bathing suit and jump into icy water? Would you slide down a snowy hill on your bare stomach? Imagine how cold that would feel! You would freeze. Penguins, however, do this all the time. Penguins swim in cold water. They slide on their bellies over ice and snow.

Riding a bicycle is a great way to get around. Bicycles are quiet, fun to ride, and you don’t need gas or electricity to make them go. You just use the power of your legs!
Bicycles have two wheels. One wheel is in front of the other. You swing your leg over the bike, sit down, and start pedaling.

The Mississippi River is the most important river in North America. It provided a major highway for early explorers of North America. Many cities grew up along it. Furs and farm goods traveled from these settlements down the river to markets. Today, more freight travels on the Mississippi than on any other waterway within the continent.