The word atrarium is not in the dictionary. Closest word would be atrium.
Definition:
- Architecture - A rectangular court, as:
a. A usually skylit central area, often containing plants, in some modern buildings, especially of a public or commercial nature.
b. The open area in the center of an ancient Roman house.
c. The forecourt of a building, such as an early Christian church, enclosed on three or four sides with porticoes.
- Anatomy - A body cavity or chamber, especially either of the upper chambers of the heart that receives blood from the veins and forces it into a ventricle. Also called auricle.
And there's astrarium in the game Dragon Age - ancient relics of Tevinter origin that allow the viewing of constellations in the stars.