Secret doors have been used in structures for thousands of years. Though in modern times we often think of them in whimsical terms due to their frequent dramatization in movies, their historical ubiquity is in fact due to their highly effective security benefits.
Some of the most fascinating secret doors can be found in the intricate passageway systems of ancient Egyptian pyramids. While the pyramids served as an ostentatious memorial of the Pharaoh, they were an obvious target for thieves. Large amounts of gold and gems were stored with each monarch so they could bring their riches to the after life. To thwart robbers the kings were buried in chambers secured by secret passageways.