Expansion Bureau is an essential prerequisite for building another town. The higher its level, the more towns you can build.
The construction of this building also allows for the recruiting of Militiamen.
| Level | Description | Population | Food | Lumber | Stone | Iron | Coin |
| 1 | 2nd Castle | 200 | 5000 | 5000 | 5000 | 5000 | 250 |
| 2 | 3rd Castle | 30000 | 30000 | 30000 | 30000 | 2000 | |
| 3 | 4th Castle | 400 | 60000 | 60000 | 60000 | 60000 | 3000 |
| 4 | 5th Castle | 600 | 120000 | 120000 | 120000 | 120000 | 4500 |
| 5 | 6th Castle | 800 | 240000 | 240000 | 240000 | 240000 | 6750 |
| 6 | 7th Castle | ||||||
| 7 | 8th Castle | 1600 | 615000 | 615000 | 615000 | 615000 | 15188 |
| 8 | 9th Castle | ||||||
| 9 | 10th Castle | ||||||
| 10 | 11th Castle | 4000 | 2510000 | 2510000 | 2510000 | 2510000 | 51258 |
| 11 | 12th Castle | 4500 | 16000000 | 16000000 | 16000000 | 16000000 | 8500 |
| 12 | 13th Castle | ||||||
| 13 | 14th Castle | ||||||
| 14 | 15th Castle | ||||||
| 15 | 16th Castle |