Alexandria is a city in northern Egypt. In ancient times, it was home to one of the world’s most important libraries. Scholars came from all over the world to study the scrolls held at the library. There were tens of thousands of scrolls there—maybe even hundreds of thousands.

But the Great Library of Alexandria is no longer standing. What happened to it? Unfortunately, no one knows. There are many different theories about how the Great Library was destroyed.

Some say that the ancient Roman emperor Julius Caesar set it on fire during a war in the year 48 BCE. Others believe that another Roman leader destroyed it in a different war over 300 years later.

Still others believe that the library was destroyed for religious reasons. The Christian leader Theodosius might have ordered the Great Library to be destroyed in the year 391. Or it might have been destroyed by Muslim conquerors in 642. We will probably never know for sure.