The North Pole is located at 90° North. It is a single dot in the Arctic Ocean where all longitudes overlap at once.
The North Pole is not a graticule in the traditional sense, since it is impossible for a geohash to fall on the latitude 90° North + offset, unless this offset is exactly zero, since nothing can be further north than the North Pole.
In accordance with the Algorithm, there is a non-zero chance for the offset being zero. This to happen, the first sixteen digits of the MD5 Hash all have to be zero. The chances for this are 1616, and with two new values per day this means it will happen 25 times every 1015 years, which is a lot more than the current age of the universe.
Should a geohash ever fall on the North Pole, it would not just be one, but 360 geohashes all in the same spot, since all longitudes overlap here. On this day the same number of geohashes would be located at the South Pole too, along with the Globalhash.
The North Pole borders 360 graticules to the South. Some of them have a page on this wiki. Those are: