We use the word "civilization" to classify groups of people throughout history. But the earliest groups -- the ancient civilizations -- set a precedent for many societies to come. Ancient civilizations had government, religion, military, art and other important social and cultural facets. So if the thought of ancient civilizations brings to mind only dusty, crumbling temples, you could use a crash course in the innovations and histories of the Egyptian, Greek and Roman empires.

From the engineering prowess of the Egyptians' pyramids to the groundbreaking Greek concept of democracy and the inventive Roman aqueducts, ancient civilizations have left an indelible imprint on our modern societies. Want to see where the action started? Explore regions of the ancient world, such as Mesopotamia, Carthage and Thebes. Get inside the minds of ancient thinkers and philosophers like Plato and Imhotep. Examine the military strategies of Cincinnatus and Epaminondas. And for a closer look at the architectural relics of ancient civilizations, study structures such as the Sphinx and the Acropolis from conception to completion.

In a time when borders expanded and contracted as military troops laid siege to mighty empires, the ancient world was dictated by mythical, powerful gods and goddesses -- nothing was left to chance. Religion was an integral part of ancient civilizations, as we see in the biographies of the statesmen, poets and military leaders who bowed to these mysterious harbingers of death, destruction and victory. Their accounts are testimony to the lasting spell the ancient world holds over us today and the events and figures that historians have dedicated their lives' work to understanding. If you're fascinated by mummies, catacombs and Zeus' pantheon of gods and goddesses in fabled Olympia, then HowStuffWorks is a can't-miss stop on your quest for insight into ancient civilizations.