The parish of Altarnun is in the Hundred of Lesneweth, in the deanery of Trigg-major and is eight miles west of Launceston. The name means Altar [church altar] of St Nonna. Altarnun Parish is now in the North Cornwall district and part of it lies within Bodmin Moor. The south-west area of Altarnun parish became part of the newer parish of Bolventor.
Altarnun can truly be described as one of the prettiest villages in Cornwall. Across two bridges stands the Church of St. Nonna. The Normans built a church here in the 12th century, but the church as it now stands was built in the 15th century, and was partly constructed of unquarried stone from the moors.
By the church gate stands a fine Celtic cross, possibly dating back to the 6th century, the time of St. Nonna herself. She was the mother of St. David and left her native Wales around the year 527.
The parish is mainly moorland, and grazed by animals, but there are areas of farmland in the Eastern areas. The river Lynher rises in this parish.
The principal villages in this parish are the churchtown, more properly called Penpont, Tredaule, Five Lanes, Gunnon, Treveage, West Carne, Trethyn, Treween, and Trewint. At Five Lanes, large cattle fairs once were held.