The street itself was once called Pole Mill Street, and the name tells you almost everything: this was the site of a working watermill complex, the Pool Mill, operating just outside the walls of medieval Dublin, powered by a river that most Dubliners today would struggle to locate on a map.

The Poddle, now largely culverted beneath the city, was the industrial workhorse of early Dublin. The Pool Mill stood on the north side of what is now Ship Street Little, just east of the Pole Gate, one of the city's medieval entry points, and close to the external face of the city wall. By 1504, the mills were recorded among the possessions of Holy Trinity, the priory attached to Christ Church Cathedral. But their history reaches back considerably further: the Dublin White Book documents a demand for arrears of rent on water-mills outside St Werburgh's Gate covering the period from around 1230 to 1319, suggesting continuous operation across at least several generations. In 1385, the same source records a grant of the mill del Poll to one Thomas Marewarde at an annual rent of thirteen shillings and fourpence. The place-name itself filtered into ecclesiastical usage: the nearby church of St Michael le Pole took its suffix from the mill-pond, as J.H. Smith observed in 1857, noting that "Le Pole" or "Le Poole" referred either to the pool from which the Castle Mills were worked, or to the river that supplied it. John Speed's 1610 map of Dublin shows the millpond and millrace clearly, running parallel to the outer face of the city wall. A city lease from 1657 still specified that the water-course, then three yards broad, must not be stopped up. When archaeologist Georgina Scally opened three test trenches at the corner of Werburgh Street and Little Ship Street over a single day in December 1992, she found up to 8.3 metres of deposits, including worked timbers likely associated with the mill or with revetting along the Poddle's re-channelled 13th-century course, as well as barrel staves with lime accretions that may point to nearby leather tanning pits.

There is nothing to see above ground at the site today. The location, at the corner of Werburgh Street and Little Ship Street, is ordinary urban streetscape, the medieval layers sealed under metres of Georgian demolition rubble and later infill. What makes the spot worth seeking out is the layering of evidence still present in maps and documents: Speed's 1610 plan, Rocque's 1756 map of Dublin which appears to show the mill-pond still visible along the north side of Little Ship Street, and the surviving street name itself. Dublin Castle sits a short walk to the northeast, and the general area rewards slow navigation with a map that pre-dates the Georgian city.