In Evony, just like troops, there are instant build fortifications with a hero that has a high politics level. Here are the politics levels required with and without Wealth of Nations to instantly build wall fortifications.
| Fortification | Politics Level | w/ Wealth of Nations |
|---|---|---|
| Traps | 607 | 486 |
| Abatis | 745 | 596 |
| Archer Towers | 826 | 661 |
| Rolling Logs | 965 | 772 |
| Trebuchets | 1066 | 853 |
http://evonyexperts.com/2011/02/instant-construction-wall-defenses/