The doctrine of unity of opposites lays in the centre of the debate on Heraclitus’ philosophy. The present article proposes a critical analysis of the mainstream interpretation of geometrical oppositions (fragments DK 22 B 59, B 60 and B 103) as mere examples of different points of view. Instead, we suggest that these fragments are fundamental pieces in Heraclitus cosmology and that they are traces of a circular and archaic paradigm. Indeed, cyclical formulations are spread throughout the fragments and, read (...) in connection with geometrical oppositions, perform a useful model to describe how permanence and change can be complementary events. In this context, circularity can be a key to the comprehension of unity of opposites as a result of interchangeable processes – as day and night, life and death, beginning and end – so that opposites are part of a concrete and vital unity. (shrink)