The first thing you see arriving in Nenagh is the cylindrical limestone keep that rises in the middle of the town - over thirty metres high, sixteen metres across at the base, one of the finest surviving Norman keeps in Ireland. It was begun by Theobald Walter, first Baron Butler, sometime in the 1190s and completed by his son around 1220. Theobald had been granted the lordship of these lands - traditional territory of the O'Kennedy clan - by King John of England, and named Chief Butler of Ireland in the same grant. Nenagh was where the Butler power began. From here, in the fourteenth century, the family moved their main residence to Gowran in County Kilkenny, and then in 1391 they bought Kilkenny Castle and held it as the seat of their power for the next five hundred years. Nenagh Castle is the cradle of that dynasty. Renovations completed in 2013 made the keep accessible again to visitors.

Beside the castle stand the ruins of one of the richest medieval religious houses in Ireland: the Franciscan Friary at Nenagh, founded in 1252 during the reign of Henry III of England. The friary became the head of the Irish Custody of West Ireland, a regional administrative centre for the Franciscan order. The medieval Annals of Nenagh - one of the named chronicles of Irish history, covering events of the thirteenth and fourteenth centuries - were written here by friars who watched the world from this small Tipperary town and recorded it. The friary survived in some form until the Dissolution of the Monasteries under Henry VIII, after which it was suppressed and gradually ruined. Today the east gable with its narrow lancet windows still stands, and at the edge of town the medieval Priory of St John at Tyone preserves another fragment of fourteenth-century ecclesiastical Nenagh.

The handsome 1843 Nenagh Courthouse, designed by John B. Keane in classical revival style, dominates Banba Square. Across from it is the old jail with its distinctive octagonal governor's residence - now a heritage centre - and beyond that the 1895 Town Hall, designed by the town engineer Robert Gill in plain cut Lahorna stone with Portroe slate. One of the local notables not commemorated in any square is John Toler, first Earl of Norbury (1745-1831), born in Nenagh and known to legal history as the Hanging Judge - a judge of such ferocity and political bias that he conducted the trial of Robert Emmet in 1803 with what one historian called open contempt for the proceedings. He sentenced Emmet to death by hanging, drawing and quartering. Toler was loathed in life and is not loved in memory. The other son of the courthouse, the architect Robert Gill, was the father of Tomás Mac Giolla, who in the 1980s became leader of the Workers' Party of Ireland and later Lord Mayor of Dublin. Nenagh has produced both ends of every political spectrum.

Patrick Collison was born in Nenagh in 1988. With his brother John he co-founded the payments company Stripe, which by 2026 was processing trillions of dollars annually and was valued among the most highly capitalised private technology companies in the world. The Collisons grew up just outside the town. Shane MacGowan, lead singer of The Pogues, was born in 1957 to Tipperary parents and spent much of his childhood in Nenagh with his extended family before the family moved to England. His best work - Fairytale of New York, A Pair of Brown Eyes, Rainy Night in Soho - lives now as one of the central bodies of Irish popular song. He died on 30 November 2023; his funeral was held at St Mary's of the Rosary Church in Nenagh. Two very different sons of one small market town, both internationally famous, both born within a generation of each other.

South of Nenagh rises the Silvermine Mountain range, with Keeper Hill at 694 metres as the highest peak. The name is not metaphorical: silver was mined here intermittently for over seven hundred years, along with copper, lead and zinc. Nineteenth-century mine workings still scar the slopes. The largest operation, the Mogul of Ireland mine at Silvermines village, closed in 1982 after processing roughly twelve million tonnes of ore over two decades and leaving environmental contamination that took the Irish state until 2009 to remediate. The pollution affected local cattle and the small River Yellow that drains into the Nenagh River. Today the area is quiet again; the mountain looms in the south as a reminder that what looks like landscape was, until the very recent past, also industry.

Nine kilometres northwest of Nenagh, the Nenagh River empties into Lough Derg at Dromineer - a small village that becomes, in summer, the busy sailing and watersports centre of central Ireland. Lough Derg is the largest lake on the River Shannon, twenty-five miles long, fed and drained by the river that defines Ireland's geographic spine. From Dromineer pier on a clear day you can see across the lake to the County Clare shore: low blue hills, the cruisers and yachts laid up at moorings, and the occasional Shannon barge - some still working - moving slowly south towards Killaloe. The town of Nenagh sits inland from this water but oriented towards it; the road from Banba Square down to Dromineer is one of the loveliest short drives in Munster, and at dusk in midsummer the light off the lake catches the keep of Nenagh Castle from kilometres away.