The path mostly runs along the railway trackbed, except for a
section under the "Greta Viaduct" which carriess the A66 bypass round Keswick.
That section of path rises above the original track level and goes round the crown of a headland and under the road
The railway used to go through that headland in a tunnel, known
as "Big Tunnel".
That tunnel still exists, but has been infilled
and sealed to prevent any collapse which might damage it or weaken the foundations of the road viaduct.
It has been inspected internally from time to time and found to be in good condition.
The entrance arch at the eastern (Penrith end) of
the tunnel is partly visible.