You can teleport your city to the alliance headquarters by following these steps:

-Tap the Alliance icon at the bottom of the screen.
-Select "Territory".
-Tap the "Territory Building" tab at the top of the screen.
-Select one of the built alliance headquarters, then tap "Go".
-You will be instantly directed to the alliance headquarters on the map, tap on the ground, then press  "teleport."

You can use the "teleport" item if available, or purchase and use Diamonds to confirm the teleport.