Deep underneath Grand Central Terminal lies a secret basement which held the power generators that ran the entire station above, and the entire Metro North railroad.
In World War II, in order to slow America’s entry into the war, Hitler and the Nazis sent saboteurs to try and destroy the converters by sneaking into the basement and simply throwing sand into them.
The northeastern railway was crucial to transporting troops and weapons to the ports, so had the converters been sabotaged, the entire course of history could have been altered. Despite armed guards standing watch, a German spy worked in the sub-basement. He recognized its importance and told Adolf Hitler, who then sent Nazis over on U-Boats in the middle of the night, armed with an interesting weapon–sand. Throwing sand into the rotating blades would have wiped the converters out, along with 80 percent of troop and supply movement. Thankfully, the Coast Guard spotted the Nazi spies up near Maine and alerted the FBI, who arrested the men just as they were nearing Grand Central. Two of them were executed, and to this day, the location of the substation remains secret.