This photo journey starts at Arth-Goldau, the junction station shown in Swiss main stations.

A pair of quadruple-system Bombardier TRAXX F140MS locos belonging to Swiss private operator Crossrail just left Arth-Goldau with an intermodal train while a class RABe 526 (Stadler Flirt) on an S-Bahn commuter service descends on the mainline of regional railway SOB

The entire mountainside on the picture, which also carries Arth-Goldau station a kilometre further back, is the rubble of the Goldau Mountain Slide. This was one of the largest landslides in recorded history: a rain-destabilised mountaintop of about 40 million m³ (0,04 km³) rushed into the valley on 2 September 1806, burying multiple villages and killing 457 people. Even after rolling down a kilometre, some rather large stones remained in the rubble.

Looking from the window of a Zurich-bound InterRegio (IR) train at the same location as above

Most of the rubble is covered by farmland and forests, though; you wouldn't tell at first sight that the entire landscape is not two centuries old.

Above: an SBB RABDe 500 just left Arth-Goldau and recedes on a southbound ICN service

Below: the SOB RABe 526 earlier on its descent to Arth-Goldau

The rubble of the landslide forms a saddle between the large pre-Alpine lakes of Zug and Lauerz. The landslide actually reached and shrunk the latter, which is barely visible through the haze on the southward-looking photo below.

An SBB 460 with a northbound IR nears Arth-Goldau

After rounding Lake Lauerz to the north and east, the Gotthard railway crosses over to the eastern shore of Lake Lucerne. Here the lake is flanked by an extremely steep mountain-side. Due to the narrow space and the danger of rock-slides, the 1882 rail line was built with several longer tunnels.

A northbound freight train between two tunnels north of Flüelen

In fact the footpath I wanted to walk along was closed due to rock-slides. (I reached the above location on the pedestrian & biker lane along the country road, which also passes through tunnels, but I didn't go past the first because it was incredibly noisy and stinky inside.)

When the second (currently southbound) track was constructed in this section, engineers decided to route it across just two very long tunnels (opened in 1943 and 1947), thus the two tracks separate.

Above: an SBB RABDe 500 recedes on the older route along the lakeshore on a northbound ICN service

Below: another SBB RABDe 500 just left the tunnel on the newer route and recedes on a southbound ICN service

Near the southern tip of Lake Lucerne, the railway passes the lakefront promenade of picturesque town Flüelen.

SBB Re 4/4^II 11305 and a sister with a very short freight below the Sacred Heart of Jesus Church. In spite of the medieval walled church impression, this is Art Nouveau from 1912

From here on, the line follows the ever narrower valley of the Reuss river. Near Erstfeld is the portal of the 57 km Gotthard Base Tunnel (GBT), where I visited the exhibition centre on my second journey. The tunnel is scheduled to open in June 2016, and track-laying was already well-progressed from the north. The old line will also be re-routed to have a junction directly at the tunnel exit, with one track passing over the portal in a virtual flyover.

Above: looking north towards the curve where the new line will join the old one

Below: the ugly concrete portal of the bi-tube tunnel. In front, machines prepare the asphalt sub-grade for one track of the old line re-routing

South of Erstfeld starts the steep climb to the old Gotthard tunnel (the "northern ramp"). I already documented it with photos of my summer tour, but here are some different scenes, on photos shot on a single day during my autumn tour (which included the only multi-hour sunny period).

SBB Re 6/6 11668 and an SBB Re 4/4^III, a common pairing for the Gotthard route also dubbed "Re 10/10", just started their heavy climb with a southbound intermodal train

At Amsteg, the Gotthard railway passes its first major viaduct, above the exit of the gorge of the Chärstelenbach creek. On my autumn trip, I climbed into the clouds on the serpentine road to the south-east of the viaduct.

An SBB RABDe 500 on a northbound ICN service

South from Amsteg, the Reuss is in a gorge, too (the Intschitobel), and the railway soon crosses it atop the next major viaduct (below which you can see the highway viaduct crossing the gorge in the opposite direction). The Sun began to shine when I got here.

An SBB RABDe 500 on a southbound ICN service

At the village of Intschi, the valley makes a nice big curve, and along the footpath on the opposite valley side, there is a viewing platform.

An SBB Re 4/4^II with a northbound train from Milan made up of EC coaches of the Italian State Railways (FS). This was a replacement for a defective tilting train

Landslides and rock-slides magnitudes smaller than the Goldau Mountain Slide are a constant threat to the railway. Near Gurtnellen, in June 2012, a 2,000 m³ rock-slide came down just when workers were trying to secure a destabilised rock wall, killing one and forcing a four-week total line closure. A year later, I photographed the now part blasted, part secured rock wall and the repaired tracks from the bus window (sorry for quality).

I return to the most-photographed spot on the line, the big curve next to the lower of the two horseshoe curve tunnels at Wassen. When I was there, workers were also busy securing the rocks above the exit of the tunnel.

Above: tilting train SBB ETR 470 003 just exited the spiral tunnel and recedes on a northbound EC service from Milan

Below: SBB Re 4/4^II 11200 exits the horseshoe curve tunnel with a northbound IR

I finish with some nice geometry at the southern end of Wassen station (which isn't served by passenger trains any more):

An SBB RABDe 500 recedes on a "northbound" ICN service, here actually southbound due to the line looping back on itself

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