Mary Celeste
The Mary Celeste was an American merchant brigantine found adrift and crewless in the middle of the Atlantic Ocean on December 4, 1872. The ship's only lifeboat was missing, but the ship itself was undamaged and its provisions had not been ransacked. None of the seven crewmen or the captain were ever seen again. Theories have ranged from waterspouts to attacks by deep-sea creatures.
Mirny Diamond Mine
The Mirny diamond mine, also known as "The Mir", is the second-largest mine in the world. It is located in Siberia and operated from the 1960s until the early 2000s. No outsiders can enter the town without a permit, and Russia forbids helicopters from flying over the mine for fear that the air currents would cause the formation of a vortex. There are a number of unsubstantiated reports that some aircraft have actually been sucked into the vortex, never to be heard from again.