The king or queen of the empire lives in the Palace. Only one Palace can exist in your realm at a time. You need a Palace in order to proclaim a village as your capital.
A palace can give a maximum of three expansion slots at levels: 10, 15 and 20.
Requirements: Main Building Level 5, Embassy Level 1
Cannot be built in a World Wonder village.
Note:
For detailed costs, bonuses, and requirements of all buildings and resource fields, you can use this Building upgrade calculator.