With its elaborate system of narrow passes, viaducts and rock-hewn tunnels, the Swiss rail network has set the standard for more than a century, since its engineers first laid tracks up and down the steepest slopes and seemingly defied the impossible.

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The first thing Ms. Bower saw when she visited the building was "the large white bubble" located on Second Avenue, a "muck house" used to store rock bored out for subway tunnels.

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Soon the window glass becomes cool to touch as the train climbs more than 1, 000 metres into a bare, otherworldly landscape of boulders and snowdrifts, navigating beautiful but treacherous mountain country through high passes and tunnels hewn from solid rock.

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Construction workers push carts on rail tracks, left over from mining days, through seemingly endless tunnels carved through metamorphic rock, while scientists head straight to their lab spaces, spotless and chilly in their fresh coat of white paint.

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His first feat: diverting the powerful river through four mammoth tunnels drilled into the solid rock of Black Canyon.

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Further into Epiros, the architectural wonders of the Egnatia Odos start to come to life, with tunnels disappearing for miles into solid rock and the inevitable danger signs flashing over the roads zigzagging the cliff-tops.

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Carved from the rock underneath the city of Rabat, likely beginning around the 3rd Century, the tunnels show how rural family burials took place among Christian, Jewish and Pagan communities.

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