We hail a cab to take us to the Union Station on a bright, sunny morning in Denver. We are to board the California Zephyr for one of the most iconic train journeys anywhere in the world. It will take us from Denver in Colorado to Emeryville in California, a 3,924km journey past the Rocky and the Sierra Nevada mountain ranges the Gore, Byers and Glenwood canyons the Winter Park resort the Truckee river and the Donner lake and the heritage town of Martinez (which claims to be the birthplace of the martini).

