On the island of Malta is a prehistoric underground megalithic structure known as the Hypogeum of Hal-Saflieni.
It was discovered by accident in 1902 when some workers were digging a hole and broke through the ceiling. They found about 7,000 skeletons, all clustered near the entrance.
The three-level underground structure is made entirely out of megalithic stones, and no one knows who or why it was built. What surprised people even more was when they found out that male voices could reverberate throughout the entire complex if the person was standing in a certain spot. Even more peculiar: the effect only worked if the speaking voice was in the 95 to 120 Hz range, so women’s voices don’t usually generate the same effect.
If you’re a man chanting at roughly the 110 Hz frequency, the entire temple complex turns into this bizarre trance-inducing room that seems able to stimulate the creative center of the human brain.
Simply put, by merely standing inside that temple complex while someone was chanting in the proper location, you actually enhanced your religious experience. And that’s all we really know about this place. We have no idea who built it or how they pulled it off. All we know for certain is that they had a knowledge of acoustics that is still baffling scientists to this very day.