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Old timber buildings, a village lunch and a possible Matterhorn view can make Zermatt the whole outing. Fast rail connections through Visp can put the village around the edge of a two-hour journey from the Lake Thun area, but check your actual date: engineering work or replacement buses change that calculation. Cars stop at Täsch, with a transfer still to come.
The Matterhorn Express and the onward lifts towards Matterhorn Glacier Paradise add travel after arrival in Zermatt. Allow time to reach the valley station, ascend and return. This is a longer mountain day, not a two-hour summit promise. The Glacier Express is a different train journey entirely.