The inspired and highly original young Irish architect John Millar designed this building in 1839. He had trained under Thomas Hopper an eminent London architect of the mid 19th Century. Portico is probably unique in having a double fronted reproduction of the ancient Greek Temple of Nemesis.
Under each portico the central columns are in-filled to make a gallery vestibule at one end and what is now the organ loft at the other. This is a highly novel solution to the vagaries of Irish weather and one that had not previously been executed.
Internally, the building has an elegant coffered ceiling and, at each end, ionic columns of the Bassean order set in antis between square pilasters. These are painted to resemble Sienna Marble as is the “noble rostrum” - the pulpit.
There are three stained glass windows - at the rear an original window attributed to Thomas Willemont and at the front two windows by the Ward Brothers commemorating those who served and those who fell in the First World War. The organ case, based on the Choragic Monument of Lysicrates, was installed as part of the 2015 restoration.