What survives above ground amounts to a single vaulted room, tucked between Capel Street and Arran Street East, yet this remnant belongs to a religious complex that once controlled landholdings stretching as far as Westmeath, Galway, Roscommon, Mayo, and Cork.

St. Mary's Abbey was founded in 1139 as a daughter house of the Benedictine Order of Savigny in France. When Savigny merged with the Cistercians in 1147, the abbey came under Cistercian rule, passing through the jurisdiction of Combermore in Cheshire before a 1156 charter placed it under Abbot Ranlulf of Buildwas in Shropshire. At its greatest extent the monastery's lands covered some 1,200 hectares, and its monastic grange, the working farm attached to the abbey, formed a triangular block of territory whose boundaries can still be traced in the modern streetscape along Bolton Street, Dorset Street, Drumcondra Hill, Parnell Street, and Ballybough, a footprint made visible in John Speed's map of 1610. The dissolution of the monasteries brought the complex down, and much of its stonework was subsequently quarried for other purposes, including the construction of Essex Bridge in 1687. What remained of the chapter house, the room where monks gathered daily to hear readings and conduct community business, was excavated in 1886, revealing a stone-built coffin beneath the floor and fragments of inlaid and incised floor tiles near the south transept. The chapter house itself is rectangular, measuring 14.3 metres by 7.1 metres, with four rib-vaulted bays whose moulded ribs are cut from Dundry stone, a limestone quarried near Bristol and shipped across the Irish Sea. A portion of the cloister arcade turned up unexpectedly in 1975 during demolition work on a seventeenth-century wall in Cook Street; those fragments are now stored at St. Audeon's Church nearby.

The surviving chapter house, a National Monument in state care, sits on Meetinghouse Lane off Mary's Abbey, and can be visited during the summer months when access is permitted. The three lancet windows that once lit the east wall are now blocked, so the interior is dimmer than it would have been, but the rib vaulting remains largely intact and the Dundry stone can still be distinguished by eye. Visitors with an interest in the abbey's scattered remnants might also look in at the Carmelite Friary on Whitefriar Street, where a medieval statue of the Blessed Virgin is believed to have originated at St. Mary's, and at St. Audeon's on High Street, where the cloister arcade fragments are held.