1. What unique masonry technique was used by the Incas to build Machu Picchu without mortar?

2. Why were the minarets of the Taj Mahal designed to lean slightly outward?

3. What is the name of the narrow, 1.2-kilometer-long gorge that serves as the main entrance to Petra?

4. What does the Arabic name 'Alhambra' translate to in English?

5. In which room of Versailles was the 1919 treaty ending World War I signed?

6. What is the popular nickname of Himeji Castle due to its white walls and elegant shape?

7. What is the most common geometric shape of the basalt columns at the Giant's Causeway?

8. What material covers the exterior of the Guggenheim Museum Bilbao, giving it its shimmering, scaly appearance?

9. The roof of the ArtScience Museum is designed to collect and recycle which natural resource?

10. What is unique about the 'The Loupe' floor at the top of the Space Needle?

11. Times Square was originally known by what name before being renamed in 1904?

12. What was the cause of the fire that destroyed the original Globe Theatre in 1613?

13. What makes the Tower of Hercules unique among all other Roman lighthouses?

14. What is unique about the construction of the churches in Lalibela?

15. What is the primary engineering benefit of the Shanghai Tower's 120-degree spiral shape?

16. Unlike the Panama Canal, why does the Suez Canal not require a system of locks?

17. What natural barrier made escaping from Alcatraz nearly impossible for inmates?

18. The 272 steps and massive golden statue at Batu Caves are dedicated to which deity?

19. What material used in the construction of the Theater of Epidaurus is responsible for its incredible acoustics?

20. The Falkirk Wheel uses which scientific principle to stay perfectly balanced?