Founded by a Viking king around 1030, with the largest crypt in Ireland or Britain underneath it — and, in a glass case down there, a mummified cat and rat.
Older than the city around it
Founded around 1030 by Sitric Silkenbeard, the Norse-Gael king of Dublin, as a wooden church. It was rebuilt in stone by the Normans from 1172 under Strongbow, whose tomb is in the nave — or rather, a fourteenth-century replacement is, the original having been crushed when the roof and south wall collapsed in 1562.
Like St Patrick’s, it was comprehensively restored in the Victorian period, this time paid for by the whiskey distiller Henry Roe, who spent a sum that ruined him. Roe’s architect took considerable liberties, and how much of the medieval fabric is medieval is a live argument.
The cathedral stands on Wood Quay, which is the site of the Viking town. When the corporation built its civic offices next door in the 1970s, the excavation uncovered one of the most important Viking sites in Europe — and then poured concrete over it anyway, over the largest heritage protest in Irish history. Twenty thousand people marched. The offices were built.
The crypt
The largest medieval crypt in Ireland or Britain, running the entire footprint of the cathedral, and it is early twelfth century — older than almost everything above it.
It holds an odd and rather good collection: the stocks from the cathedral’s manorial court, a tabernacle and candlesticks from the brief period when James II held Catholic services here in 1689, statues of Charles II and James II removed from the old Tholsel, and the cathedral’s silver.
And the cat and the rat. Two mummified animals found in an organ pipe in the 1860s, the cat apparently having chased the rat in and both having become stuck. They are dessicated, alarming, and beloved. Joyce refers to them in Finnegans Wake. Locals call them Tom and Jerry.
The bells
Nineteen bells, one of the largest rings in the world, and they are rung by a volunteer band. If you are nearby on a Sunday morning or a practice night you will hear them across the whole south inner city.
Dublinia
A covered stone bridge from the cathedral leads to Dublinia, a Viking and medieval Dublin exhibition in the old Synod Hall. It is aimed at families, it is well done, and a combined ticket is available. If you have children it is the better half of the visit.
Practical
Admission charge for visitors, free for services. Choral evensong is sung several evenings a week.
The two cathedrals are four hundred metres apart and a combined visit is a straightforward morning.
More History
Kilmainham Gaol
The prison where the leaders of the 1916 Rising were executed, and where a great deal of modern Ireland was decided. Guided tour only, and it books out weeks ahead.
St Patrick's Cathedral
The largest church in Ireland, built where Patrick is said to have baptised converts, with Jonathan Swift buried in the floor and his epitaph on the wall.
Glasnevin Cemetery
A million and a half people buried in 124 acres, including most of the names in modern Irish history, and a guided tour that is one of the best things in the city.