Angkor Wat
A 12th-century temple so grand that it ended up on a national flag, and so well made it outlasted the empire that built it.
Stonehenge
Stonehenge's smaller bluestones were hauled an estimated 150-plus miles from Wales, and no one has settled exactly why.
The Eiffel Tower
A "temporary" 20-year structure that Paris just... never took down, and is now unimaginable without.
Petra
Petra is an ancient city carved straight into rose-colored sandstone cliffs, and its famous Treasury was probably a royal tomb.
The Taj Mahal
History's most famous love letter was written in marble and took more than twenty years to finish.
The Great Wall of China
A 2,000-year, multi-dynasty construction project so vast that no one has ever fully agreed on exactly how long it actually is.
The Pyramids of Giza
The Great Pyramid was the world's tallest man-made structure for about 3,800 years, until a medieval English cathedral topped it.
Machu Picchu
A royal Inca estate so well-hidden in the Andes that the Spanish conquistadors never even found it.
The Colosseum
Under the Colosseum's arena floor, a hidden underground network let gladiators and animals appear out of nowhere mid-show.