Circles

1/100 sec @ f11, ISO100, 66mm (zoom), Canon 20D

A fair enough representation of a circle I think

1/160 sec @ f11, ISO100, 28mm (zoom), Canon 20D

Kind of circles within circles here, from the outer rim, to the shadow of the rim to the ripples.

1/60 sec @ f3.5, ISO1000, 51mm (zoom), Canon 5D

Enough overgrowth of a flower pot to feature as an implied circle.