Stores metal and crystal.
It is cheap to build but takes a bit of time. When all your Warehouses are full from gathering resources from Mines, you will receive a one-time message:
ℹ️ 💎 Crystal storage is full.
ℹ️ 🔩 Metal storage is full.
Nevertheless, you can temporarily store more resources in certain situations:
In these cases, resources will be depleted at 10,000 per minute until it reaches your maximum storage.
See Resources for a summary on how each resource works.