Leaning Tower of Pisa

The famous Leaning Tower of Pisa is an architectural marvel. The building has stood for over 800 years on unsolid ground. While most buildings build with faulty foundations fall over, the Tower of Pisa managed to remain standing because the ground solidified just enough under its foundation to prevent a catastrophic failure, and modern engineers have reinforced its structure (https://www.youtube.com/watch?v=HFqf6aKdOC0).