Mountjoy can boast being Dublin's only true Georgian square, each of its sides being exactly 140 metres in length. While the North, East and West sides each have 18 houses, the South has 19, reflecting some variation in plot sizes. Though each side was originally numbered individually, the houses are now numbered continuously clockwise from no. 1 in the north-west corner. While its North and South sides are continuous from corner to corner, the East and West sides are in three terraces, interrupted by two side streets, Grenville Street and Gardiner Place to the West and Fitzgibbon and North Great Charles Street to the East. Gardiner Street passes through the West side of the square, while Belvidere Place and Gardiner Lane run off the North- and South-East corners.