in architecture, continuation of the aisled spaces on either side of the nave (central part of the church) around the apse (semicircular projection at the east end of the church) or chancel (east end of the church where the main altar stands) to form a continuous processional way. The ambulatory often provided improved sites for the numerous altars for saints, which formerly were located along a crowded corridor behind the high altar; the altars are reached through circular arches piercing the curved outer wall of the ambulatory.