Markree Castle, 17th-century castle in Collooney, Ireland

Markree Castle is a grey stone castle in Collooney, County Sligo, with a rectangular main block, a projecting central bay of tall mullioned windows and a battlemented parapet with corner turrets. A low stone wall with a metal gate and a small white sign stands before the paved driveway. The River Unshin partly moats the building, which has 30 guest rooms reached by a carved wooden staircase from the hall.

The property came into the hands of the Cooper family in 1663 after Cornet Edward Cooper acquired it during the period of Cromwell's campaigns. The castle retained its structure over the centuries and was later converted into a residence.

The Cooper family tree is traced in a large stained glass window on the staircase landing, running from Victorian times back to the reign of King John. The dining room carries Louis Philippe-style plasterwork. The castle's Irish name is Caisleán Mharcréidh.

The castle stands in Collooney, County Sligo, with the River Unshin running past the grounds. Inside, a monumental staircase leads to a hall, and a carved wooden staircase continues to the 30 guest rooms. The 300-acre estate holds red squirrels, otters and kingfishers, so allow time to walk the grounds.

In the 1830s, a major telescope was housed here in a private observatory on the estate grounds. This facility enabled several astronomical discoveries and made the castle a scientific center of its era.