Cristobal Piers Mole. The building at the end of the mole was the control building for the ship degaussing station. This was a large magnetic coil on the bay bottom which when the ships passed over it, it demagnetized them to counter magnetic mines. The  bunkers on the berm is a 90mm AMTB battery. This is a rare view of four fixed mount 90mm guns in one battery.  Info provided by Andrew W. Fraser and Terry McGovern.