Why does the Colosseum have holes in it?

What you see of the Colosseum today is really only it's skeleton. Originally it's face (or outer shell) was finely carved marble. It was too expensive to make the entire building of marble, so it was used only to beautify the outside of the edifice and certain areas of the interior as well. read more

The exterior of the Colosseum is covered with holes. The truth about their origin is that the blocks used for the exterior of the building were held together by iron clamps. These iron clamps were taken out in later times (Decline of Rome) and reused for other purposes. read more