The Peristasis was a four-sided porch or hall of columns surrounding the cella

Cella

A cella or naos , is the inner chamber of a temple in classical architecture, or a shop facing the street in domestic Roman architecture...

 in an ancient Greek peripteros

Peripteros

Peripteros is the special name given to a type of ancient Greek or Roman temple surrounded by a portico with columns. It refers to the useful element for the architectural definition of buildings surrounded around their outside by a colonnade on all four sides of the cella , creating a four-sided...

 temple. This allowed priests to pass round the cella (along a pteron

Pteron

Pteron is an architectural term used by Pliny the Elder for the peristyle of the tomb of Mausolus, which was raised on a lofty podium, and so differed from an ordinary peristyle raised only on a stylobate, as in Greek temples, or on a low podium, as in Roman temples....

) in cultic processions. If such a hall of columns surrounds a patio or garden, it is called a peristyle

Peristyle

In Hellenistic Greek and Roman architecture a peristyle is a columned porch or open colonnade in a building surrounding a court that may contain an internal garden. Tetrastoon is another name for this feature...

 rather than a peristasis. In ecclesial architecture, it is also used of the area between the baluster of a Catholic church and the high altar (what is usually called the sanctuary or chancel

Chancel

In church architecture, the chancel is the space around the altar in the sanctuary at the liturgical east end of a traditional Christian church building...

).