A alliance depot.

Alliances are groups of players that cannot attack each other, working as a team. You can also give alliance members resources, which can be helpful to them. Alliances can be created in the Alliance Depot which requires 999 or each resource, which is fairly a low price. You can also join a alliance. However, there is a limit to how much people can be in a alliance. Only up to 50 people can join a alliance, and you can only be in one alliance at a time. If you request to join a alliance, that alliance makes a decision whether to decline your request, or accept your request to join.