Halfway between Belfast and the border town of Dundalk sits Newcastle, a seaside resort in County Down that has quietly rebuilt itself into one of Northern Ireland's best bases for the outdoors. It's about an hour's drive from Belfast, an hour from Dundalk, and roughly two from Dublin — but it deserves more than a day trip.

The town's headline act is the Mourne Mountains, whose highest summit, Slieve Donard, tops out at 2,789 feet — the tallest peak in Northern Ireland. The classic climb starts in a mossy forest of oak, birch and pine, crosses a mile-long valley of wild grass and grazing ponies, then follows an old stone wall up the steep final ascent. On a clear day you can see Wales, Scotland, the Isle of Man and Donegal from the top; on a bad one, you might not see your own hand. Weather in the Mournes turns fast, so pack waterproofs in every season.

If one peak isn't enough, the Mourne Seven Sevens — nicknamed the Seven Peaks — starts and finishes in Newcastle. It's a 19-mile loop with more than 8,000 feet of elevation gain, linking seven summits (Donard, Commedagh, Bearnagh, Meelmore, Meelbeg, Binnian and Lamagan), all but one above 2,300 feet. Expect boulder fields, jagged granite ridgelines and sea views over the green patchwork of rural Ireland.

Back at sea level, golf is the other big draw. Royal County Down's Championship Links has been ranked the best course in the world by Golf Digest — ahead of Augusta National, Pebble Beach and Pine Valley — and currently sits at No. 3 with Top 100 Golf Courses. Unlike many elite American courses, visitors can actually play it, on both the Championship Links and the Annesley course. Green fees are pricey and tee times are limited, so submit an online enquiry well in advance.

Round out a stay with Murlough Beach and Nature Reserve, next to the golf course. A boardwalk threads through the dunes, home to rabbits and more than 600 moth and butterfly species, while seals and wading birds show up along the bay. The five-mile beach holds Blue Flag status and suits anything from a brisk morning walk to a very bracing Irish Sea swim.

For travellers, Newcastle works on several levels: a serious hiking hub, a bucket-list golf stop, and an easy coastal escape with good pubs on the main street and the upscale Marine & Lawn Slieve Donard Hotel if you want comfort after a day in the hills. It pairs naturally with Belfast or Dublin, but it's worth its own nights on the itinerary.