The Old Store stood against the old northwest city wall, on a site opposite the west end of the present building.

[2] The cathedral was extended and modified many times over its history – it was initially to a square footprint, with later extensions to both the east and west ends of the building.

[2] Bishop John Power made some of the most significant additions – in 1881, he commissioned the baldachin, and a new altar (incorporating the front of its predecessor) and reredos.

[2] The cathedral's fine stained glass windows were installed between 1883 and 1887, most commissioned from Mayer of Munich.

In the final major 19th century modification, a classical, Ionic-form cut-stone external west facade was installed during Bishop Sheehan's time.

These rods monitor the movement of the columns, which are built on the marshy foundations of the cathedral site.

A new altar was installed so that Mass could be celebrated ad populum (facing the people) – this altar incorporates carvings from the sanctuary of St Carthage's Church, Lismore – 'a sensitive gesture to earlier history'.

The action was changed to tubular pneumatic, the key compass extended and a detached draw-stop console added, and a large hydraulic blowing plant installed.

Significant tonal and structural changes were made, the action converted to electro-pneumatic, the compass extended, and a detached stop-key console installed.