Part of the Sahara A to Z series
High up on the side of a remote High Atlas valley is an engineering marvel – hewn through the cliff face a spiral tunnel manages to curl down through the rock and emerge underneath itself.
I was told about this curiosity in 2012 by the chap at the cozy Chez Moha auberge (right) in Aït Youb while researching the second edition of Morocco Overland. Riding a BMW F650GS, I followed his directions with the usual route-finding issues and then, beyond the last village, hacked up a stony disused track to the 2250-m (7340′) Tagountsa Pass. From the cliff edge I recall the timeless view stretching east up the Plain d’Amane valley towards Rich, pictured below and on p128 in the current book. A short distance later I spun through the tunnel and rolled down a series of switchbacks back to the valley floor and a tasty tajine back at the auberge.
Spiral tunnels have been a long-established solution to constricted route building challenges across mountains. You could even say that your typical complex freeway intersection where the road winds back under itself to change direction tightly is the same thing in flyover form. But you must admit that hacking out any type of tunnel – let alone one where there’s no room to dig out a regular switchback – is an impressive task.
Not for the first time on this website, I’m able to benefit from research of Yves Rohmer (right) on his always fascinating collection of old Saharan curiosities at Saharayro, including the Tagountsa tunnel. Viewed on Google Earth, the big picture is more vividly rendered setting View > Historical Imagery back a few years.
Even then it’s hard to visualise what’s happening until you look at the old plan, right. You can see the anticlockwise descent of the bore and just work out that it starts with a short separate concrete bridge over the lower mouth of the tunnel. The daylight streaming down the gap can be seen in the image repeated on the left (and as a slim shadow in the round inset, above)
Built in 1933 over a period of just three months by some 3000 labourers from local and French regiments, few realise that at this time the French were still fighting to subdue renegade Berber tribes in the mountains of Morocco.
As you can see on Yves pages, the engineers, sapeurs and legionnaires passed their spare time commemorating their achievement by engraving regimental emblems in and around the structure. I was told the motivation for all this effort was to enable a secure, high transit of the valley, so avoiding protracted Berber ambushes at the narrow Imiter Gorge (left; ~KM70) with it’s Mesa Verde-like dwellings.
The same crew probably built the better known 62-metre Tunnel de Legionnaires five years earlier at Foum Zabel now on the main N13 highway north of Errachidia. A plaque there boldly states:
“The mountain barred the way.
Nonetheless the order was given to pass…
The Legion executed it.”
The Tagountsa tunnel the Legion helped build is at KM102 on Route MH13 in the book, though if you reverse the route it’s only a 10-km off-road drive off the Rich road just east of Amellago, turning north onto the dirt at KM113. Depending on storm damage, an ordinary car or a big bike should manage it, but note that you’ll be negotiating all those hairpins on the Google image above. From the west side (as Route MH13 describes the loop) it was a rougher and slightly more complicated ride on the BMW up to the pass.
Perhaps because trains can’t negotiate hairpins or climb very steep grades, it seems that spiral or helicoidal tunnels have been a much more common feature on mountain railways than roads, particularly in the Rockies.
Norway’s Drammen Spiral (left), some 50km southwest of Oslo is a notable example, dug we’re told, as an alternative to disfiguring effects of open quarrying on the landscape back in the 1950s while at the same time producing a revenue-producing tourist attraction in the process.