Knocknahillion

Knocknahillion is one of the Maumturk Mountains of Connemara in County Galway, Ireland. At 607 m, it is the 210th–highest peak in Ireland on the Arderin list, and 256th–highest on the Vandeleur-Lynam list. Knocknahillion is in the middle sector of the long north-west to the south-east spine of the Maumturks. The summit is offset to the west of the rocky central ridge of the Maumturks, and its western-facing slopes have a distinctive "diagonal" rock stratification when viewed from the Inagh Valley.

Naming
Irish academic Paul Tempan notes that Knocknahillion derives its name from the townlands of Illion and Illion West. It is to the west of the central spine of the Maumturks range at a point where the range turns to a more south-easterly direction (like an elbow).

Geography
Knocknahillion is in the middle sector of the long north-west to south-east central spine of the Maumturks range in Connemara.

To the north, Knocknahillion is connected to Letterbreckaun, the 2nd highest peak in the range at 667 m, by a high winding rocky ridge that includes the subsidiary peak of Knocknahillion North Top at 541 m, whose prominence of 38 m qualifies it as an Arderin. Further along this ridge lies the minor peak of Barrlugrevagh at 558 m, whose prominence of 17 m qualifies it as an Arderin Beg.

To the southeast of Knocknahillion is the col of Maumahoge (Mhám Ochóige), which then rises up again to the corrie lake of Lough Maumahoge (Loch Mhám Ochóige), and eventually to Binn idir an dá Log, the highest mountain in the range at 702 m.

Hill walking
The easiest way summit Knocknahillion is a 5-kilometre 2-3-hour route via the pass of Maumahoge; however, because of its positioning on the high rocky central spine of the central Maumturk range, it is also summited in a longer 14-kilometre 5-6 hour loop-route starting at the col of Maumahoge in the south, climbing Knocknahillion and then along a winding 2-kilometre rocky ridge to the top of Letterbreckaun, before descending via the sharp "v-shaped" col of Maam Turk (Mám Tuirc, meaning "pass of the boar"), from which the entire range bears its name.

Knocknahillion is also climbed as part of the Maamturks Challenge, a 25-kilometre 10–12 hour walk over the full Maumturks range (from Maam Cross to Leenaun), which is considered one of the "great classic ridge-walks of Ireland", but of "extreme grade" due to the circa 7,600 feet of total ascent; however, because the peak of Knocknahillon is offset to the west of the core winding rocky ridge, it is not always summited during the challenge.

Rock climbing
While the Maumturks range is not particularly known for rock climbing routes (unlike Bencorr and its Carrot Ridge spur, across the Inagh Valley), some have been developed at a crag just below and west of Lough Maumahoge (L876 532), with routes of 90 to 190 metres at climbing grades of S to HVS.