14 Mysterious Landmarks That Science Still Can't Fully Explain

6. The Great Zimbabwe (Zimbabwe): Africa's Mortar-less Citadel

The vast stone ruins of Great Zimbabwe, flourishing between the 11th and 15th centuries, stand as a testament to a powerful African civilization, yet much of its purpose and decline remain scientifically unexplained. The site's most remarkable feature is its massive dry-stone walls, built entirely without mortar, some standing over 30 feet tall and 16 feet thick. The sheer scale and precision of this masonry, creating a sophisticated urban center, defies earlier colonial theories of foreign builders. Its abrupt abandonment also remains shrouded in mystery, challenging historical assumptions.