The Big Bang happened at the "north pole" of spacetime. Eventually all matter and energy will reach the "south pole" and recombine. The Big Crunch theory will never die!
The big bang happened at the center of the universe and every point of space is the center of the universe at all times. You could argue that the center of spacetime is definitionally the Big Bang since that’s when time is believed to have started to exist in the first place but we don’t have a good grasp of how to define the center of a 4D physical structure where one dimension is time which doesn’t seem to really act like the other dimensions.