In OLYMPIA's Dynamo Room, the underside of the protective deck can be plainly seen. The space apparently also served as an ammunition handling room, since the ammunition hoist for the forward turret ends at this space, as do hoists for other guns. The ammuniton was apparently raised vetically to this level, and the  moved horizontally to the appropriate hoist. The reason for this space with its required horizontal movement of ammuniton was to prevent an enemy  projectile or an accidently dropped shell from falling directly into the vicinity of the magazines themselves, In other words, the hoists did not connect the magazines to the topside level of the ship directly.
 

Entering the space via ladder, the visitor will find themselves in a fairly open space, with space for the various pieces of electrical apparatus. Ventilation ducts run along the underside of the protective deck, which angles down forming the exterior bulkhead of the space. directly aft of the ladder by which the visitor enters is the ammunition hoist for the forward turret. Aft of that is the hoist leading down to the handling room and magazines below.