An architectural term referring to an open space in a building or a shaded walk or an enclosed area in front of a building: The vineyard owner wanted his new home reflecting the ancient xystum that he remembered from his home in Italy.

A xystum can refer to a wall, a promenade (pedestrian walk area), an alley, or an open path.

The xystum may also refer to an atrium (open space in a building), ambulacrum (walk planted with trees), or parvis (enclosed area) in front of a basilica or a public building in Roman times.