What is the center stone of the arch called?

Related questions

1. How much water did aqueducts carry?
2. What is a better word than adequate?
3. What is a word for more than enough?
4. How much water do you really need?
5. How did a Roman aqueduct work?
6. What is a synonym for adequately?
7. What are the benefits of aqueducts?
8. How much water should I drink daily?
9. Why is aqueduct Spelt with an E?
10. What word means more than adequate?

Tags

1. #known
2. #cases
3. #generally
4. #position
5. #during
6. #wedge
7. #shaped
8. #stone
9. #locks
10. #piece
11. #construction
12. #allowing
13. #keystone
14. #masonry
15. #stones
16. #round
17. #vault
18. #weight
19. #placed
20. #final
21. #capstone