You can build new buildings from the construction menu.
What types of buildings are there?
- Civilian buildings (eg. for increasing the population)
- Military buildings (eg for recruiting units)
- Fortifications for improving defense
- Decorative items for improving pubiic order
As soon as you click on a building, you can upgrade it, move it anywhere, and even demolish it to make room and retrieve some building materials.
The upgrade level of your Keep determines how fast buildings are constructed and upgraded.