AMTK 133 leads the California Zephyr through the evergreens of Plainview, Colorado.

AMTK 133 leads the California Zephyr down the grade of Big Ten Curve.

AMTK 189 (P42DC) leads the California Zephyr past the Rocky Siding as it heads to Arvada, Colorado.

The California Zephyr, lead by AMTK 52, heads towards Big Ten Curve as a BNSF oil train that has just past through the landmark curve gets ready to head towards Denver.

Amtrak’s westbound California Zephyr climbs out of Rocky, Colorado, on July 4, 2005. Above the train in the background is the east switch of Clay siding.

Amtrak’s California Zephyr meets a westbound BNSF freight at Rocky, Colorado, on the afternoon of June 28, 2014. In the background is the city of Denver, where train 6 will be making a station a... (more)

A long Union Pacific coal train makes its way around Big Ten Curve as it drops down the 2% grade while rounding the wide 280 degree curve.

A winter wonderland greets riders of the California Zephyr as AMTK 189 (P42DC) leads the train around Big Ten Curve, which will drop the train 2% along the 280 degree curve.

The morning California Zephyr gets ready to pass a waiting BNSF oil can train which has pulled off onto a siding just after the Big Ten Curve to let the Zephyr pass.

A fresh layer of snow has blanketed the foothills and trees as Amtrak 130 leads the California Zephyr up the Moffat Tunnel line and into the Colorado Rocky Mountains.

Led by Southern Pacific GE AC4400CW Nos. 314 and 182, a westbound Union Pacific coal empty approaches Big 10 Curve west of Rocky, Colorado, on the morning of August 4, 2001.

Ansco’s Rio Grande Ski Train approaches Big 10 Curve between Rocky and Clay, Colorado, on the morning of August 4, 2001. Summer editions of the passenger train operated to Winter Park for hikers... (more)

AMTK 76 (P42DC) rounds the Big Ten Curve as it leaves Denver and the Front Range behind. Soon the California Zephyr will be climbing through the Colorado Rocky Mountains on its way to Emeryville,... (more)

The Big Ten Curve enables UP 6049 (AC44CWCTE) to drop further in altitude, winding through the 270 degree switchback which keeps the grade change at 2%.

UP 6049 (AC44CWCTE) leads a coal train through Big Ten Curve as it drops in elevation towards Arvada, Colorado.