Storing stuff in caves with drones

There are a number of advantages to storing things in caves: the potentially vast area relative to surface land costs; the lack of construction necessary; the constant temperature; the inherent security (provided all the entrances to the cave system are know). But they can be dangerous, and hard to navigate (uneven surfaces, etc).

Enter drones. Inaccessibility / navigation is drastically improved with UAVs. And there's no hazard to human health. The cave system can easily be mapped by UAVs, and watertight packages deposited throughout the system.