It appears on John Speed's 1610 map of Dublin city, drawn clearly enough to be recorded, yet its precise location has never been pinned down. The street today is busy and ordinary, flanked by the National College of Art and Design and St. John's Church, and nothing in the immediate environment announces that a medieval crossing once sat somewhere nearby.

Speed's map, one of the earliest detailed cartographic records of Dublin, shows the bridge spanning a watercourse that ran along Thomas Street between St. Catherine's Church and John's Lane West. That watercourse was not incidental; it powered a series of medieval watermills belonging to St. John's Priory and Hospital, the religious institution that gave the surrounding area much of its early character. A priory in this context was a community of monks or canons under a prior, often with associated charitable functions, and St. John's combined monastic life with the care of the sick and poor. The mills would have ground grain, and the bridge gave access across the mill-stream to St. John's House, positioned to its south-west on the same map. The watercourse itself has since been culverted or absorbed entirely into the city's infrastructure, leaving no visible trace.

There is nothing to stand in front of here in the conventional sense. The site is an absence rather than a presence, which is itself part of what makes it worth knowing about. A visit to the area around the National College of Art and Design and St. John's Church on Thomas Street, combined with a look at Speed's 1610 map, gives a reasonable sense of the general vicinity. The map section, which shows the bridge and watercourse running between two still-recognisable landmarks, is the closest thing to a primary document the site has. For anyone with an interest in how medieval Dublin managed its water infrastructure, or in how much can vanish beneath a busy urban street, the stretch of Thomas Street between those two landmarks is a quiet place to consider what the cartographic record preserves when the ground itself does not.