Frankly, the judging in this year's World's Biggest Moat contest wasn't even close. Certainly there were a number of solid contenders, including a few in London, but the winner took Gold in a massive landslide. No, no, that's not it. I meant, flood. A massive flood. Yeah, that's it.
Mont Saint-Michel wins this contest hands down.
Historically, a moat is just a deep ditch filled with water that surrounds a castle, fortification, or town meant to inconvenience attackers. It was a somewhat effective strategy, but no one took the idea as far as these monks in France (albeit, unintentionally).
The medieval abbey, Mont Saint-Michel, was built near the English Channel in Normandy. As a result, every 18 years or so, it involuntarily secedes from mainland France. (see photo)
It seems that the gravitational pull of the sun and moon alter tidal patterns causing “super tides” which cut off the abbey from their usual wine, cigarette, and frommage deliveries.
It's pretty cool looking until you consider that it's probably just a harbinger of watery things to come. According to predictions, this event will happen again on March 3, 2033, but by then you might be able to see something eerily similar just by staring out your own window.