Macgillycuddy's Reeks is Ireland's highest mountain range, encompassing 11 of the country's 14 summits that exceed 900m in altitude. The name dates from the 18th century – the MacGillycuddy clan were local landowners, and 'reeks' is dialect meaning 'stacks' (a reference to the layered nature of the rocks here).
The usual approach to the hills is from Cronin's Yard, where there's a car park (€2), tearoom (packed lunches available on request), showers and toilets, a free basic campsite and a couple of nifty camping pods. It's at the road's end (OS ref 836873), reached from the N72 via Beaufort, west of Killarney; follow signs for the Gap of Dunloe at first, but keep straight on where the Gap is signposted left. After 4km you'll reach Kissane Foodstone and petrol station; 50m further on, over the bridge, Cronin's is signposted on the left (a further 3km from Kissane). The Killarney Shuttle Bus runs here twice daily.
There's an alternative trailhead at Lisleibane – continue past the Cronin's Yard turnoff for 1.5km and turn left (signposted Carrauntoohil Lisleibane) on a narrow winding road which ends after 2.5km at a large parking area (free).
You can get a taste of the Reeks at close quarters by following the waymarked loop trail from Cronin's Yard into Hag's Glen, the beautiful approach valley that leads to loughs Callee and Gouragh below the towering east face of Carrauntuohil (round-trip 8km).
There are several routes up Carrauntoohil (1040m), Ireland's highest peak, but none of them is easy. Even the most straightforward requires good hill-walking and navigation skills, while others are serious scrambling or rock-climbing routes. The traditional route to the summit is via The Devil's Ladder, a gruelling trudge up a badly eroded and unpleasantly loose gully path at the far end of Hag's Glen. The easiest descent is via the Zig-Zags to the east of the Devil's Ladder.
An alternative route ascends via Brother O'Shea's Gully (some rock scrambling and good route-finding ability required), a steep and challenging route through spectacular scenery on the mountain's north side. Experienced hillwalkers can follow the directions in Adrian Hendorff's guidebook, The Dingle, Iveragh & Beara Peninsulas: A Walking Guide. If you're in the slightest bit unsure, hire a guide – Kerry Climbing and Hidden Ireland Adventures both offer guided ascents of Carrauntoohil year-round, weather permitting (booking is essential).
Climbing Carrauntoohil should never be attempted without a map and compass (and the skills to use them), proper hillwalking boots, waterproofs and spare food and water. Use Harvey's 1:30,000 MacGillicuddy's Reeks Superwalker map, or the 1:25,000 Ordnance Survey Adventure Series map (MacGillicuddy's Reeks & Killarney National Park).