The California Zephyr #6 train rounds the Big Ten Curve in Rocky, Colorado as it heads to Denver on the Moffat Tunnel Sub.

Amtrak engine #146 (P42DC) exits Tunnel #1 at Plainview, Colorado as it leads the California Zephyr #6 train towards Denver.

The California Zephyr runs east on the Moffat Tunnel Sub towards Rocky, Colorado and will soon be backing into Denver's Union Station.

The California Zephyr passes maintenance equipment working on the Big Ten Curve in Rocky, Colorado.

With the Denver skyline in the upper right, Amtrak engine #146 (P42DC) leads the California Zephyr out of Tunnel #1 at Plainview, Colorado. The train will soon arrive in Denver and take on and di... (more)

The Amtrak Winter Park Express Ski Train rounds the corner in the North Yard as it takes a load of skiers from Denver to the Winter Park ski resort.

The Winter Park Express Ski Train runs through Leyden, Colorado at sunrise on the Moffat Tunnel Sub.

Amtrak's Winter Park Express Ski Train runs through the snow towards the platform at the ski resort to pick up passengers for the ride back to Denver, Colorado.

The Winter Park Express Ski Train runs through Leyden, Colorado at sunrise.

Dawn's early light catches the Amtrak Winter Park Express Ski Train passing Blue Mountain Road and heading through Coal Creek Canyon on the Moffat Tunnel Sub.

The temperature is -4 degrees, and the snow is falling as the Winter Park Express heads back to the ski resort's platform to pick up passengers for the ride back to Denver.

The Winter Park Express Ski Train leaves Denver at sunrise and will run into the Colorado Rocky Mountains on a two-hour trip to the ski resort on the west side of the Moffat Tunnel.

The sunrise glints off the Amtrak's Winter Park Express Ski Train as it runs past the old water tower in the North Yard at Denver, Colorado.

The Amtrak Winter Park Express Ski Train runs through Coal Creek Canyon on the Moffat Tunnel Sub

The Amtrak Winter Park Express Ski Train rounds the base of Blue Mountain as it heads into the Colorado Rockies on the Moffat Tunnel Sub.