What has made these lines across the landscape?

According to local legends these lines were created by Fionn MacCumhail, or Fingal the Giant, a mythical Celtic warrior-king. The glen (mountain valley) used to be heavily wooded, so Fingal built a set of roads through the forest so he could hunt deer while riding on horseback. It is said the marks on the mountainside are the remains of these roads.

This explanation is not generally used today, but the real story behind these ‘roads’ is no less fascinating.

At the end of the last Ice Age, approximately 13,000 years, a glacier blocked the lower parts of Glens Roy, Gloy and Spean (a glen is a mountain valley). The ice acted like a dam, trapping water behind it and forming a large loch (or lake).

Formation of 260m Parallel Road


The water filled the Glen to a height of 260 metres; it could not rise any higher than this as a low point between two hills allowed the water to escape.

The waves of the loch, and continual freezing and thawing of the water at its edge, carved a beach into the sides of the mountains. We can see the remains of this beach today as the lowest ‘road’ at 260 metres high.


 But why are there three ‘roads’ here?


Rise and Fall

Between 100 and 200 years after the first beach was established the temperature dropped. More ice formed, and the glacier advanced up into Glen Roy, blocking off the overflow point between the two hills.

As a result the loch became deeper, and its waves carved another beach into the mountainsides, higher up this time at 325m. The water could not rise higher as there was a second overflow point at this height. Excess water drained into the neighbouring valley Glen Spean.

Formation of 325m Parallel Road









After another 100 or so years passed, the temperatures dropped again. This caused the glacier to advance further up Glen Roy and blocked off the second overflow point. Once again the depth of the loch increased and a third new beach was formed at a height of 350m.

Formation of 350m Parallel Road









When the climate eventually warmed up, the ice melted and the glacier retreated. The overflow points were unblocked in reverse order, so the loch drained away. The beaches cut into the mountainside are a ghostly reminder of the three stages of this long-vanished loch.

The Parallel Roads today










Diagrams © Ted Hatch


The lie of the lines

Glen Roy © Helen Rawling RGS-IBG Discovering Britain

Glen Roy viewpoint

Cast your eye across the valley. Do you notice anything unusual here, particularly on the slopes to the left-hand side?

If you look carefully you should be able to see that there are three lines running in parallel, sometimes they fade into the mountainside but in other places they are quite distinct. They have become known as ‘parallel roads’.

What has made these lines across the landscape? Click to reveal the answer

Location: Car park and viewing point just north of Bohuntine, off A86 Roy Bridge, Highland PH31 4AH
Grid reference:

NN 29803 85339

Glen Roy viewpoint credits

Thank you to:

Helen Rawling for creating and photographing the viewpoint 

Ted Hatch for drawing the diagrams

Glen Roy - Gleann Ruaidh in Scottish Gaelic - means 'Red Glen'