Castletroy Castle, also known as The Black Castle can be seen on the banks of the Mulcaire River. Many versions of the name exist in Irish such as Caisleán an Treoigh or Caladh Uí Threo which means O' Troys landing place, or O' Troys Callow (marsh or meadow).
It was erected in the reign of Henry 111 (1216-1272) by one of the O' Briens. Many years later it was the seat of the Mac Keoghs, a war like tribe, often in conflict with neighbouring chiefs.
The Earl of Desmond was overlord of this territory but lost this title after the rebellion against Queen Elizabeth in 1583 and the Desmonds never ruled here again.
Accordind to tradition Ireton set up cannons on Harty's Hill in 1651 and battered the castle. It was owned at that time by The bourkes of Brittas and Castleconnell. However the Bourkes were dispossessed of their lands in 1641 when they sided with confederates against the English and were transported into Connaught during the Cromwellian plantation. This castle was granted to James Duke of York in 1666 and later sold to the Hollow Blade Company in 1703.
Castletroy Castle's history is recounted in verse in Hogan's "Lays, Legends of Thomond"
Castletroy by war,
Tide and time batter'd
Stands, like an old chief
With his armour all shatter'd
As if musing, in gloomy and gaunt desolation
On the red feudal days
When Green Erin was a Nation.
There the warlike Mac keoghs,
In their power and revell'd
And often in fight
Were their sounding spears levell'd
'Till Cromwell, the fiend, with his
Ploughed their strong castle walls
On the brink of the Shannon".