Ambulatory

The ambulatory is a place for walking, designed beyond a row of columns to allow believers and visitors to walk around Notre-Dame Cathedral’s apse and nave. Notre-Dame de Paris actually has a double ambulatory around the nave, characterized by a double row of columns which form the side aisles. 

When the building was enlarged in the 13th century, chapels were placed around the side aisles. These double aisles and the double ambulatory of the choir are a unique example in medieval religious architecture.