The Mournes are a relatively youthful set of granite mountains, which explains why their comparatively unweathered peaks and flanks are so rugged, forming steep sides, moraines and occasional sheer cliffs. Closer up, these give sharp, jagged outlines; but from a distance they appear much gentler, like a sleeping herd of buffalo. The wilder topography lies mostly in the east, below Newcastle, although the fine cliff of Eagle Mountain (636m), to the southwest, is wonderful if you can afford the time and effort to get there, and the tamer land above Rostrevor has views down into Carlingford Lough that rival any in Ireland.
In summer at least (winters can be surprisingly harsh), there are plenty of straightforward hikes in the Mournes that require no special equipment, with obvious tracks to many of the more scenic parts. There are also, of course, more serious climbs and climbing courses in the Mournes are run by the Tollymore National Outdoor Centre in Bryansford (whttp://www.tollymore.com), but they must be booked well in advance.