From Denver to Glenwood Springs by Train.

Amtrak's California Zephyr runs from Chicago to San Francisco — 2,438 miles, the longest daily route in the entire Amtrak system. The most beautiful section of the whole journey is the stretch between Denver Union Station and Glenwood Springs. Five and a half hours, 157 miles, through the Moffat Tunnel, the Gore and Glenwood Canyons, and along the upper Colorado River. If you have a day to spare, this is the trip.

The train leaves Denver Union Station every morning around 8:00 AM. The station itself is worth showing up early for — Beaux-Arts construction from 1881, restored as a transit hub and city centerpiece, with shops, bars, restaurants, and the Crawford Hotel inside it. Coffee at Pigtrain Coffee, breakfast at the station market, and then onto the platform. The Zephyr pulls in on time.

The first thing to know about the California Zephyr is that the seats are not the point. The point is the Sightseer Lounge — the observation car with floor-to-ceiling windows, swivel chairs facing the view, and a small café below. Get there early and stake a seat. Veterans of the route say to grab one within fifteen minutes of departure. Once Denver is behind you, the lounge is the entire reason you came.

The Moffat Tunnel.

About an hour and a half out of Denver, the train climbs steadily up into the foothills, crosses the South Boulder Creek, and then enters something dark and long. This is the Moffat Tunnel — 6.2 miles straight through the Continental Divide, opened in 1928, the highest railroad tunnel in North America at 9,239 feet of elevation. For about ten minutes the train is in total darkness. When it emerges on the other side, you're in a different country.

Vasquez Ridge at Winter Park Resort comes up on your left, abrupt and stunning against the blue sky. Ski runs cut down the mountain. The train continues north through the Fraser River Valley, with Highway 40 visible from the right side of the train. If you've driven that highway before, you'll recognize sections from a totally new perspective.

Byers and Gore Canyons.

The Colorado River appears alongside the tracks somewhere around Granby, and from this point on, the train and the river are companions for the rest of the trip. Byers Canyon comes first — a tight passage between sheer red walls. Gore Canyon follows, deeper and more dramatic, with the river running fast below and the railway clinging to a ledge cut into the rock. Most highway routes don't pass through this country at all. The train and the river have it almost to themselves.

The first time I rode it, a retired couple from Florida sat across from me in the lounge. They had never seen snow-capped peaks before. They didn't speak for an hour. They just looked.

This is also the section where the Sightseer Lounge fills up and the seats get harder to come by. If you stepped away to grab a sandwich, your seat is probably gone. Plan accordingly.

Glenwood Canyon.

The final and most spectacular stretch is Glenwood Canyon. The walls rise up to 2,000 feet above the Colorado River on both sides. Interstate 70 runs split-level along one bank — a twelve-year, $490 million engineering achievement that's still considered one of the great American highway projects — and the train tracks run along the other bank, low to the river. You can see the highway from the train. The drivers can see you. There's something funny about waving at someone in a car from the window of a train, knowing they'll be at Glenwood Springs in an hour and you'll be there in three.

Bighorn sheep appear on the rocks. Eagles overhead, sometimes. The river runs fast and clear. Mt. Sopris, the twin-summit peak that anchors the southern half of the Roaring Fork Valley, comes into view in the distance.

Arriving at Glenwood Springs.

The Zephyr pulls into the Glenwood Springs Amtrak station — a small, walkable depot in the heart of downtown — sometime in the early afternoon. And here is the genuinely remarkable part: the station is steps from the world's largest hot springs pool. A pedestrian bridge over the Colorado River leads directly from the train depot to Glenwood Hot Springs Resort. No car required. No taxi needed. You get off the train and you can be in the hot water inside fifteen minutes.

The Hotel Colorado is on the same side of the river as the pool, also walkable. The Hotel Denver is on the downtown side, across the bridge. The whole town is set up for the train traveler in a way most American towns aren't anymore.

The Trick: Sit on the Right.

The single most useful piece of advice I can give about the California Zephyr is about which side of the train to sit on. Going westbound from Denver, the Colorado River is on your left for most of the canyon sections — but the climb out of Denver into the Rockies is best from the right side. The Sightseer Lounge solves the problem by giving you views in both directions. If you can't get a seat in the lounge, the right side of the train wins out for the first half, and the left for the second.

Going back eastbound the next day, switch sides. The same scenery looks completely different from the opposite angle.

What to Bring.

The dining car is fine. The snack bar is fine. The truly experienced California Zephyr riders bring their own food. A small cooler with sandwiches, fruit, cheese, and a thermos of coffee will outlast anything Amtrak can sell you on board, and at a fraction of the price. Bring a book you don't actually intend to read — you'll spend the whole trip looking out the window.

WiFi exists on the train but is intermittent at best. In the canyons, it disappears completely. Download anything important before you board. Cell signal does the same — strong near towns, gone in the mountains. This is, in the end, part of why the trip is good. For five and a half hours, the world stops being able to find you.

The Return.

The eastbound train back to Denver leaves Glenwood Springs in the late afternoon — usually around 5:30 PM. You can do the trip as a day-out: arrive at 2 PM, soak in the hot springs for two hours, walk through downtown, eat an early dinner, and get back on the train. But this misses the point. The pool is open until 10 PM. The Hotel Colorado is steps away. The right way to do this trip is to spend the night.

Stay at the Hotel Colorado for the history, or at the Glenwood Hot Springs Resort Lodge for unlimited pool access and complimentary breakfast. Soak in the morning, breakfast in the lobby, and catch the Zephyr east in the afternoon. Two days, no driving, all of it spent looking at things.

The full California Zephyr runs all the way to Emeryville, near San Francisco. From Glenwood Springs west, the train descends through Grand Junction, into Utah and the Wasatch Range, across the Great Salt Lake, into Nevada, and finally over the Sierra Nevada at Donner Pass. That's a different trip — a 52-hour, two-night, country-spanning journey. But the Denver-to-Glenwood Springs section is the highlights reel. If you only do one piece of the Zephyr, do this one.