What do I need to upgrade Castle to lv22?

You need to have mint level 21

Traven level 21

food - 28 M

Marble - 57 M

Iron - 42 M

Wood- 28 M

Gold - 21 M

Population - 210K

For mint 21 your house should be on 21

You need two upgrades for Food storage, Marble storage, Iron storage.