We booked the trip over email a few months back, and paid on the day. We travelled from Realp to Gletsch by steam then changed to diesel down the hill.
Only thing to be aware of is the train leaves from a seperate station in Realp which is about 10 minutes walk from the MGB one.
We had reserved seats in the front coach, the guard even came down to tell us what was going on as we were the only non German speakers on the train, this was a very nice touch.
The train stopped at Furka for about 20 minutes and we sampled some excellent cake and cheese.
The trip was very expensive 146sfr for the pair of us for a single ticket, but well worth it.
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