Yes, you can complete the entire Glacier Express journey in a single day, as the full route from Zermatt to St. Moritz (or vice versa) takes approximately 8 hours. The train travels through 91 tunnels and across 291 bridges, offering a continuous panorama of the Swiss Alps. Most travelers catch the morning train around 8:00 AM or 9:00 AM and arrive at their destination in the late afternoon. However, "doing it in one day" requires you to already be in Zermatt or St. Moritz the night before, as adding a connection from Zurich or Geneva on the same day makes for a very long 12-to-14-hour itinerary. In 2026, it remains one of the world's most popular "slow" express trains, and because it is a single-day journey, seat reservations are mandatory and often sell out months in advance for the peak summer and winter seasons.