The O'Reilly coat of arms

Northern Ireland in 1530, showing the O'Reillys territory.

The remains of Cavan abbey today. Giolla Iosa Rua O'Reilly founded the abbey in 1300. Cavan town grew around it.

Clough Oughter castle built on a small island in Lough Oughter (about 5 miles east of Cavan town) was the main seat of the O'Reillys until the late 1300s.

Shantermon hill was the inauguration site of the chief of the clan, known as "The O'Reilly".