Hemicycle

n.	1.	A half circle; a semicircle.
	2.	A semicircular place, as a semicircular arena, or room, or part of a room. The collections will be displayed in the hemicycle of the central pavilion. - London Academy.

Noun

1.

hemicycle - a plane figure with the shape of half a circle Synonyms: semicircle

plane figure, semicircle, two-dimensional figure