NUT solutions

In 1963, Ezra T. Newman, Theodore W. J. Unti and Louis A. Tamburino, in the mid-1960s discovered a bizarre solution to Einstein's equations. The solution they found was so weird that they dubbed it the "NUT solution". This solution allows for closed timelike curves and time travel. 

NUT solutions allow a strange kind of time travel and allow for a strange distortion of space. On the surface, the solution resembles a typical black hole. However, if you took a trip around this black hole, 360 degrees, you would not return to where you started. You would wind up on another sheet of the universe. The topology of a NUT universe is like a spiral staircase.