Fitting shapes together
This photograph from the air of Mountstuart Primary School in Cardiff Bay shows that the two buildings are like round cakes with slices taken out.
When you look closely you can see they are not round but have many straight sides. They are made of triangles that point towards the centre and fit together perfectly. The buildings would have 16 identical triangles to make a 16-sided polygon if the ‘slices of cake’ were all there. (If you imagine a line across the middle you can see that half the building has 8 complete triangles.)
The more sides a polygon has, the closer it gets to a circle. The designers have created the feeling of a circle using straight walls that are much cheaper to build than curved ones with curved glass in the windows.