The former Rossmore family estate, opened to the public in 1974 and now run by Coillte as a forest park. Several waymarked loops thread through old beech and oak woods, with views over Monaghan from the higher paths and ornamental lakes in the lower ground. The drumlin landscape — rounded glacial hills, one after the other — is one of the easiest places in Ireland to see this kind of terrain at work.
The ruins of Rossmore Castle, once a vast Gothic Revival mansion with 53 rooms and (famously) 117 chimneys, sit in the centre of the park. Most of it was demolished in the 1970s after years of neglect, but the footprint and some walls are still visible. Free entry, useful for a couple of hours of fresh air.