| Knocknahillion | |
| Other Name: | Cnoc na hUilleann |
| Elevation M: | 607 |
| Elevation Ref: | [1] |
| Prominence M: | 152 |
| Listing: | Marilyn, Hewitt, Arderin, Simm, Vandeleur-Lynam |
| Translation: | hill of the elbow |
| Language: | Irish |
| Location: | County Galway, Republic of Ireland |
| Range: | Maumturks |
| Coordinates: | 53.5218°N -9.704°W |
| Map: | island of Ireland |
| Map Relief: | yes |
| Grid Ref Ireland: | L8703653756 |
| Topo: | OSi Discovery 37 |
| Geology: | Pale quartzites, grits, graphitic top bedrock |
| Easiest Route: | Via pass of Maumahoge |
Knocknahillion [2] is one of the Maumturk Mountains of Connemara in County Galway, Ireland. At 607m (1,991feet), it is the 210th–highest peak in Ireland on the Arderin list,[3] and 256th–highest on the Vandeleur-Lynam list.[4] [5] Knocknahillion is in the middle sector of the long north-west to the south-east spine of the Maumturks.[5] 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.[5]
Irish academic Paul Tempan notes that Knocknahillion derives its name from the townlands of Illion and Illion West .[2] [6] 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).
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 667m (2,188feet), by a high winding rocky ridge that includes the subsidiary peak of Knocknahillion North Top at 541m (1,775feet), whose prominence of 38m (125feet) qualifies it as an Arderin.[5] Further along this ridge lies the minor peak of Barrlugrevagh at 558m (1,831feet), whose prominence of 17m (56feet) qualifies it as an Arderin Beg.[5]
To the southeast of Knocknahillion is the col of Maumahoge (Irish: Mhám Ochóige), which then rises up again to the corrie lake of Lough Maumahoge (Irish: Loch Mhám Ochóige), and eventually to Binn idir an dá Log, the highest mountain in the range at 702m (2,303feet).[5]
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 (Irish: Mám Tuirc, meaning "pass of the boar"), from which the entire range bears its name.[7] [8] [9]
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",[8] 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.[9] [10] [11] [12]
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.[13]