3. The Leaning Tower of Pisa, Italy
The Leaning Tower of Pisa once faced imminent collapse due to its notorious tilt and unstable foundation. For centuries, engineers and architects feared the iconic structure would topple. A massive 20-year stabilization project ultimately saved the tower, using innovative techniques to halt its lean without erasing its unique charm. Completed in 2001, this feat of engineering preserved a beloved symbol of Italy. Read more about the rescue at BBC.
