A village's builders live in the Main Building. The higher its level, the faster your builders will complete the construction of new buildings (up to 50% of the building time).  

Furthermore you can upgrade your village in your Main Building to a city. The city has a value roughly equal to that of two villages. The city has higher loyalty (200%), a Water Ditch, an increased population and production of culture points, as well as Resource Fields that can be upgraded up to lvl 12.

When you have buildings queued for construction and your main Building is destroyed or upgraded, the building times will not be recalculated.

Demolishing If you do not need a building any more, you can order your builders to demolish it. This requires a Main Building at level 10 or above.