Exedra

Stoa of Attalos, Athens, 150 B.C. This photo depicts the style of a Hellenistic civic building.

(from Greek ex, 'out' plus hedra, 'seat') A seat with a high back, curved in a semicircle; also a semicircular roofed recess in a building with seats or a curved bench. (Leland M. Roth)

Unfortunately, I did not have an image of an exedra but, this public building from the same period as the exedra's origin may have had them built inside or outside. (the building was refurbished in the 1950's).