(Image: Google Maps; entrance to the Crawley Tunnel on The Mound)
Scotland Street and the hidden Leith railway tunnel aren’t the only forgotten Victorian passages hiding beneath the city of Edinburgh. The rather obscure Crawley Tunnel, an underground aqueduct running approximately from The Meadows to the foot of The Mound, is periodically unearthed during road excavations and other engineering works.
The Crawley Tunnel (or Crawley Aqueduct) was built in 1821, at around the same time as the Glencorse Reservoir. Nestled in the picturesque Pentland Hills several miles outside Edinburgh, the reservoir was built to provide water to the mills of Auchendinny, Glencorse and Milton Bridge. It also supplied drinking water to the Scottish capital. (The ruins of St Catherine’s Chapel were submerged when the valley was intentionally flooded to create the dam back in the early 19th century.)
The Crawley Tunnel is known to run to Hanover Street, in Edinburgh’s Georgian New Town, though it may extend down the hill as far as Scotland Street. From the foot of The Mound, the subterranean aqueduct passes under Princes Street, where its stone walls and arched roof were damaged and subsequently repaired during road works in 1958.
(Image: Google Maps; rough course of the Crawley Tunnel between The Meadows and Princes Street)
According to Canmore, a 50-foot-long section of the Crawley Aqueduct was exposed during more recent work on the new Edinburgh Tram network. The section of tunnel could be seen curving round from the foot of The Mound, across Princes Street and along the east side of Hanover Street.
When the works also revealed part of a second tunnel, archaeologists were brought in to examine the lost subterranean structures and chart other undocumented Victorian drains from Edinburgh’s 19th century past. This second tunnel was located immediately north of the Royal Scottish Academy (RSA), which was built around the same time as the Crawley Tunnel. Both tunnels met at the foot of Hanover Street, which may suggest that one was a re-routing of the original to accommodate construction work on the RSA.
Examination of a short accessible section of the second tunnel, which was partially filled with rubble at some point in time, revealed a doorway leading to a small chamber (3.4m by 1m in dimension). This tunnel, at 1.7m in height and 1.5 metres wide, was slightly larger than the main Crawley Aqueduct (which measured 1.4m high and 1.5m wide).
(Image: Google Maps; manhole leading to Crawley Tunnel, as shown on Canmore)
The tunnel structures had also been impacted over time through the addition of later sewage infrastructure. A concrete manhole was found to have been driven through the second tunnel, connecting to an active sewer some five metres below. Finally, once remedial work had been carried out on the sections of tunnel damaged during road and tramway excavations, the mysterious passageways were again sealed off from the outside world.
The Crawley Tunnel, which housed the original pipes bringing water from the Pentlands to the city, also passed under the Royal Infirmary of Edinburgh and the Grassmarket. Along with its subsidiary, which may have extended under the Royal Scottish Academy building itself, it represents the many layers of history that make up this fascinating city and the myriad tunnels that may also lie hidden, undocumented and forgotten, beneath the streets of the capital.
Around the same time that workers unearthed the Crawley Tunnel, excavations at Haymarket also revealed an original 19th century tram pulley room. The subterranean chamber had been built for Edinburgh’s old cable-hauled tramway before being repurposed as a large-scale air raid shelter during World War Two (more here).
If you’re a fan of Victorian Edinburgh (and perhaps slightly later), why not set out and rediscover the little-known route of the defunct Colinton industrial tramway.