For the mostpart, the railway clings to the side of the wooded gorge, crossing the 100 valleys (which gives the railway its name) on a series of stone and steel viaducts. The most impressive is very early in the journey at Verscio where the viaduct spans a gorge 75m below(see video below).
The descent to Domodossala is also quite an impressive feat of engineering with the line zig-zagging across the hillside as it loses height. At Domodossala we boarded the standard SBB express bound for Berne to travel through the Simplon tunnel, via Brig to Spiez.
The scenery after emerging from the tunnel was incredible, particularly as we could review it from different perspectives as we retraced our journey at different heights along the side of the valley.
At Speiz, we changed trains for Interlaken.
The views along the lakeside contrasted with the mountain scenery of the Lotschberg line.
We left the train at Interlaken West to find the Lotschberg Hotel, a short walk away. This was my favourite hotel of the trip. The staff were extremely friendly and helpful, there is a coffee lounge with internet access (free wifi) and the room was clean and comfortable. Furthemore, a washing machine and drier is provided for a small charge.
There was time for me to visit the Modelleisenbahn-treff, a five minute walk from the hotel. The main feature is a layout depicting many of the key railway sights in Switzerland in what appears to be 7mm scale. 50 trains run simultaneously spiralling up mountains and across the ceiling to connect with different parts of the layout. I tried following one train as it traversed the layout but lost track of it in one of the tunnels. I did spot it later in a totally unexpected part of the layout. The hour I spent there was nowhere near sufficient - and I wish now I had taken more photos and some video. I think I've talked myself into a return visit!