Whirlpools

Early November 1957 Escher finished his woodcut and wood engraving Whirlpools. He used a new printing technique for it, cutting one block which he printed on the same piece of paper in two colours.

Two rows of fish swimming head to tail fill the space. The red row has exactly the same shape as the grey one, but has been turned 180 degrees. Starting infinitely small, the fish gradually grow, removing themselves from their origins. They are at their largest in the centre, where they come within reach of the other core. They start to revolve around it, get smaller and finally dissolve into oblivion. Escher wrote to his son Arthur about it*:

‘I doubt whether the “public” will understand, let alone appreciate, what fascinating mental gymnastics are required to compose this sort of print.’

Source
[*] Wim Hazeu, M.C. Escher, Een biografie, Meulenhoff, 1998, blz. 391