The Innocent Railway path runs from Newington - St Leonard's area under Holyrood Park via Duddingston and Craigmillar to Brunstane in the East of the city. It is one of Edinburgh's extensive off-road pedestrian cycleways and part of the UK-wide, National Cycle Network's Route 1 (NCN1).
A good starting point is the tunnel itself. The Edinburgh side entrance at a new-build residential close at St Leonard's is not obvious unless you are looking for it. It looks just like another suburban cul-de-sac. But once you are on the track, it's well signposted.
The Edinburgh and Dalkeith Railway, opened in July 1831, originally as a horse-drawn tramway built to haul agricultural produce and coal from the mines of Lothian up to the Edinburgh at St Leonards. Designed by engineer James Jardine (1776-1858), it was Edinburgh's first railway line.
The line, much to the surprise of its promoters, became popular with passengers. It converted to steam locomotives after it was taken over by the North British Railway in 1845. The line probably earned its nickname "the Innocent Railway" due to its safety record: it carried 300 to 400 thousand passengers a year without fatalities, in an age where steam engines had a reputation as dangerous. It's also been suggested that the nickname stuck due to the slow pace of travel. Certainly, today, it seems an apt name for a simpler form of travelling.
When it originally opened in 1831 it was the Scottish gauge 4'6''. It changed to 4' 8½'', the present gauge, in 1845.
The 517 metre Innocent Railway Tunnel under Holyrood Park is huge, particularly when you consider it was the first railway tunnel in the UK. Before 1845, trains were winched by cable drawn by horse and stationary steam engines up the St Leonard's Inclined Plane.
The tunnel is one of three engineering features of the original 9 mile line. The other two being a cast iron beam, 18ft (5.4m) bridge and an impressive timber beam viaduct on Masonry Piers. The viaduct at Thornybank in Dalkeith was demolished in the Sixties, but you can still see the bridge at at the SE of Bawsinch Nature Reserve.
The railway line closed in 1968 and the section between Newington / St Leonard's and Craigmillar re-opened in 1981 as a pedestrian bicycle path.