Rising from a drumlin ridge in County Monaghan stands one of Ireland's most impressive medieval earthwork monuments, though you'd be forgiven for missing it amongst the deciduous woodland that has long shrouded the site.

Perched on a northeastern slope overlooking White Island and the northern shores of Muckno Lough, the site of Blayney Castle tells a fascinating tale of ambition, rebellion, and eventual ruin.

Mannan Castle at Donaghmoyne in County Monaghan tells a story of medieval ambition meeting harsh frontier realities.

Situated on a broad hill in County Monaghan, Maghernacloy Castle stands as a testament to centuries of Irish history and the complex web of allegiances that shaped the country's past.

Just off Castle Street on the eastern side of Clones' Diamond lies a hidden piece of Ulster's turbulent past.

The ruins of Mahon's castle supposedly stand somewhere on a hill in Conaghy, County Monaghan, though their exact location remains frustratingly elusive.

On a shelf towards the bottom of a northeast-facing slope overlooking White Island and the northern end of Muckno Lough sits the site of a significant early 17th-century fortified house.

The remains of Candlefort's motte and bailey castle sit on a natural shelf along the north-facing slope of a hill, roughly 300 metres north of the River Fane and 200 metres south of where St Daigh's early monastery once stood.

On a bluff overlooking a stream and bridge in Carrickmacross stands what remains of Essex Castle, a fortified house built between 1628 and 1633.

Sitting atop a drumlin in County Monaghan, this moated site at Nook offers a glimpse into medieval Ireland's defensive architecture.

Positioned on a low spur at the eastern end of Roosky Lough's northern arm, this site marks where Roosky Castle once stood, a significant stronghold of the Dartry McMahons.

Essex Castle, now incorporated into St. Louis Convent in Carrickmacross, County Monaghan, tells a story of English plantation, Irish rebellion, and religious transformation spanning four centuries.

Standing on the highest point of a drumlin ridge in County Monaghan, the motte and bailey at Clones tells a story of medieval conquest and resistance.

The castle at Monaghan represents a fascinating example of early 17th-century plantation architecture, built from the recycled stones of religious history.

In the early 17th century, Sir Edward Blayney embarked on an ambitious project to build a castle at Monaghan, recycling stone from the town's old Franciscan friary.