The winter snow show continues for an hour or so, and we pass in and out of the tunnels that were carved into the sides of the mountains when it became too difficult to run the railway track along the side of the mountain. The longest tunnel comes about two hours after we leave Denver. It's the famous Moffat Tunnel, which carved 100km off the distance by train from Denver to Salt Lake City when it opened in 1928. It's also the highest point anywhere on Amtrak's network. We rumble through, catching dust and smoke blown into the carraiges every time someone passes between the cars.
When we emerge at Winter Park, suddenly the snow has begun to recede, and the mountains are revealing more of their green forests and red earth. We pick up speed across a plateau surrounded by mountains, running alongside a river and passing through small communities that have settled here, in some of the harshest parts of the country.
Another hour passes, and there is no trace of snow. It is not just the landscape which changes on this journey - the climate and weather shifts as well, and we're soon rolling along narrow gorges and rugged valleys, high above the crashing waters of the Colorado River and far below shimmering peaks. I am left completely aghast by this scenery. In planning this trip, it was strangely the most scenic route I had the least expectations or excitement for. It's not even the middle of the day, and I am in awe of the scenery we have passed through.
The Byers and Gore Canyons pass, and sitting in the relative luxury of this train I am left astonished at the feats of endurance that explorers, immigrants and settlers would have undergone when discovering this rugged landscape for the first time. In the Sightseer Lounge Car, which has become the social hub of the entire train, we are constantly swapping seats to get better views above us and below us, and to compare details on maps and in guidebooks. I've brought my lunch with me, and I ate with my new acquaintances, our eyes fixed on the amazing landscape that we are rolling past.