| 1 | His castle in the air crumbled. | |
| 2 | Your plan is merely a castle in the air. | |
| 3 | You plan is merely a castle in the sky. | |
| 4 | Their plan is merely a castle in the air because it is simply impracticable. | |
| 5 | Football is not built on nothing - it's built on huge popularity among supporters. |