EXAMPLES FROM THE WEB FOR DECAGON
The plan of the church was a decagon, within which six composite columns in the centre supported six semi-circular vaults.
Decagon, dek′a-gon, n. a plane figure of ten angles and sides.
In the fourth are six triangles, in the fifth, five polygons from a pentagon to a decagon.
Below the arches are the chapels which surround the decagon in symmetrical fashion.