Big barracks shelter

The ramparts of the Trongsund redoubt hides rather extensive underground premises. The picture shows a large barracks shelter. Authentic plaster has been preserved on the ceiling and it's mean the roof does not leak and it's the waterproofing is in order. In those days waterproofing , usually has been done by pouring the masonry with resin, then with clay in three layers and on top of a one meter layer of earth overlaid with layers of turf was made, so that the intertwined roots would give additional protection against enemy shells.