The precipitous cliff in the photo is called Tojinbo in Fukui Prefecture, Japan. Tojinbo is consist of cooled and solidified andesite made by magma which went into sedimentary formations during volcanic activities 120~130 billions years ago. After that, they came up on the surface of the earth by wave erosion. Columnar joints were developed in andesite with hexagon in its cross section.
There is no established theory why cross section of columnar joints has hexagon shape. It is said that as a hypothesis, when andesite is cooled, cooled points is developed at even intervals and contraction occurs toward the centers of cooled points and crack occurs between those cooled points. The most efficient cracks should be happened with hexagon shape consisting of equilateral triangles. This is why you can see many hexagon surfaces on the top of the cliff.
Japan is a volcanic country and you can enjoy such tourist attractions in Japan. Mt. Fuji is also a volcano though it is inactive now.
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