Megalomaniac even more devilish stuff

Capital city: This can be any town you have under your control provided that it has a Market, Church, Castle, and Town Center. Usually the largest city under your control will be the likely candidate. This function is allowed as soon as you are made king. The capital city becomes the imperial capital when you are made emperor. The capital city gets some automatic defensive advantages to a normal town. It automatically gets a wall around and paved streets at no cost to you. When defending the capital your troops will get a bonus on damage. The bonus on damage does not apply to mercinary forces. Once you town is made a capital it's church becomes the ecclisiastical center of your kingdom and any the first priest there or created is the bishop.

Road: These greatly increase your ability to move troops and goods to other town and regions. Speed is dubbled on roads. There are three types of roads. The dirt pathc is what is first available to you. It increases movement by 10%. The leveled path increases movement by 25%. The stone road increases movement by 50%. In order to build roads and bridges you need a royal architect, yet another npc. These are created in church schools. You need to have at least one to make any roads and the more you have the faster you can build roads since you can dispatch them to different regions for construction.

Bridges: Spendy and time consumming but worth the effort. Note that both roads and bridges can be destroyed. Bridges come in two varieties. The simple trus-bridge and a drawbridge. Both take time to research. Both types can be upgraded to fortified bridges that give more hit points.
Drawbridges can be further upgraded to tower-bridges that have some offensive capabilities.

Encampments: This is really a type of stance you can order an army into. If you order your army to encamp then they will erect tents, picket there horses, and dig a trench around their paremeter. This heals them very fast and provides a defensive bonus if attacked. It takes time to encamp, similar to erecting a trebuchet. They cannot move unless given the order to break-camp.