Leave the iron on? That's nothing:

Papers among thousands of files captured from the Stasi, the secret police of East Germany, claim tons of live Second World War munitions were buried in concrete bunkers beneath the runways of Schoenefeld airport in East Berlin. It is now the main destination for discount airlines, such as Ryanair, and numerous charter companies.

Not only did the commissars intern munitions beneath the runways, but also entire Nazi fighter planes, all fuelled and fully bombed-up, according to the Stasi.

[...]

Experts believe it entirely feasible that, in the aftermath of the Second World War, with Berlin littered with millions of tons of unexploded ordnance, the Soviets could well have pressured local officials to move to clear the airfield as swiftly as possible.

To where? Easy:

Berlin, with its sandy, dry soil, was perfect for the bunker-building of the Third Reich. Hundreds of thousands of them were constructed during the 12-year lifespan of the Nazi government: for every one metre of building above ground in modern-day Berlin, there are three metres below ground.

Bunkers are being discovered every day and a group called Underground Berlin has turned several of them into tourist attractions.

We can find a modern corollary. If only twelve years - but six in relative peacetime - were needed to build what can only be described as a city writhing with a maze of bunkers that have not been fully accounted for in seventy years, imagine what hideaways Saddam Hussein was able to construct, with the help of none other than German engineers, after two decades. All this in a country the size of California, dominated by forbidding landscape. Four months shrinks in that scale a bit, doesn't it?