Noted architect William Morrison designed this building in the late 1820’s. Built in ashlar granite, it is one of Ireland’s finest examples of ancient Greek revivalist architecture. It is said to have cost £30,000 to construct. The building of the courthouse was made possible by the generous patronage of the Bruen family of Oak Park. The Courthouse, based on the Temple of Llissus in Athens, gives the impression of a temple set on a high plinth, but this obscures the fact that the basement is a maze of cells and dungeons. A cannon from the Crimean Way stands on the steps.
The architect who designed Carlow courthouse - William Vitruvius Morrison - came from a highly talented architectural lineage being the son of Sir Richard Morrison who became the most influential architect of his time. William followed in his fathers footsteps, and indeed was something of a child prodigy doing architectural designs when only fifteen years of age. William was to suffer from prolonged bouts of ill-health however, and sadly died before his father at the young age of 44 in 1838. The architecture of Carlow courthouse itself offers a lavish and imposing external architecture which later courthouses were not to incorporate due in large part to the very high costs of such extravagant designs. An interesting story is associated with Carlow Courthouse. it was apparently intended for Cork city, but the plans were mixed up and Carlow gained Cork's impressive Courthouse.