Oslo

Oslo (also known as Christiania depending on what side of town you're on) was the capitol of Norway since medieval times. At some point within fairly recent memory, the entire city and a great bit of the surrounding geography was erased from the face of the earth, leaving a very symmetrical crater. One of the few survivors of the tragedy was Othar Tryggvassen &mdash; but if he caused it, he hasn't made the fact widely known. However, there are suspicions the disaster is linked to the Great Wall of Norway, which was definitely built by Tryggvassen.