What stood here was not simply a wall but a layered arrangement of towers, a fortified house, and a water-filled ditch, all compressed into a stretch of riverfront less than two hundred feet wide. A 1585 survey recorded, with unusual precision, that the tidal Liffey came hard against the base of the wall at every spring tide, flooding up against stone that was, in places, no more than four feet thick and nineteen feet high. That the city trusted this relatively slender barrier to define its edge says something about the confidence, or perhaps the pragmatism, of its builders.

The origins of the structure go back to 1310, when a man named Geoffrey de Mortone was granted permission to build two towers and a fortified house between them at the town end of the bridge of Dublin. The Historic Atlas of Dublin City places the crenellated and turreted tower at the north-west corner of the city wall, with construction beginning in 1310 and completion recorded in 1331. A mural tower, in this context, means a tower built into or projecting from a defensive wall rather than standing independently. By the sixteenth century the site had passed into the hands of the Usher family. In 1560 and again in 1566, the Dublin Assembly Roll recorded agreements with John Ussher allowing him use of the town ditch adjoining his orchard on the west side of the wall, on condition that he keep it clean and continuously filled with water, an early example of civic maintenance contracted out to a neighbouring landowner. By 1585, the property was associated with William Usher, and a detailed survey of that year noted a "little new tower" in his garden, positioned roughly 30 metres from the Bridge Gate to the east and 43 metres from Harbard's Tower to the south-west.

Nothing visible remains above ground today, and the site is absorbed into the fabric of the modern quays. The historical record, however, is vivid enough to reward attention. The 1598 Civic Regulations for the Defence of Dublin, issued by the Mayor and aldermen on the 8th of November that year, listed the precise posts where twenty-four hired watchmen were to stand each night from six in the evening until six in the morning, and "the little new tower in Mr. Ushers background" was among them. Saint Audoen's bells were to toll as a curfew signal. Anyone walking along Usher's Quay today, with those Assembly Roll entries in mind, is essentially standing on a stretch of riverbank that once formed the armed perimeter of a medieval city, staffed nightly by armed men and lapped by the tide.