The California Zephyr makes the turn at Big Ten Curve. With the angle of the low sun the lead unit almost looks like it's about to time travel ala Back to the Future.

BNSF 8159 (ES44C4) runs downhill to the bottom of Big Ten Curve.

A long BNSF freight makes the turn at the bottom of the Big Ten Curve and heads towards Arvada, Colorado.

UP 6720 (a former Chicago & North Western AC4400CW) leads an empty coal train as it climbs Ten Mile Curve, which will lead them to Coal Creek Canyon and the first of many tunnels as they head into... (more)

A westbound Union Pacific manifest freight climbs the mesa where Big 10 Curve is located on the climb up the front Range of Colorado’s Rocky Mountains on the afternoon of June 20, 2018. The head... (more)

Rounding Big 10 Curve west of Rocky, Colorado, is a westbound Union Pacific manifest freight with lone DPU GE AC4400CW No. 6216 shoving hard on the rear on the afternoon of June 20, 2018. In the b... (more)

California Zephyr's AMTK 43 makes the turn leading to the Big Ten Curve.

Under threatening skies, AMTK 837 leads the California Zephyr through Big Ten Curve. After traveling through Rocky and Arvada it will soon pull into Denver's Union Station before eventually headi... (more)

Looking more like a roller coaster ride than an Amtrak train, the California Zephyr reaches the bottom of the hill west of Arvada and will soon enter Big Ten Curve to begin the climb up to the Roc... (more)

The California Zephyr runs down the hill from Arvada to Rocky, Colorado, passing the spur that at one time led trains to the Rocky Flats Nuclear Weapons Plant. The facility produced plutonium tr... (more)

BNSF 4262 (ES44C4) has descended from the foothills to Big Ten Curve, which will take the freight to Arvada, Colorado.

Up, up and away. BNSF 7073 (ES44DC) leads a freight on the steep climb up to Tunnel #1 as it begins the journey through the Colorado Rocky Mountains. You can really appreciate the amount of grad... (more)

With the city of Denver far in the background, a Union Pacific freight swings through “Little 10 Curve” at Rocky, Colorado, on the afternoon of June 20, 2018.

She'll be coming around the mountain when she comes.

Amtrak 837 (P42DC) has just come through tunnel #1 in the upper left and continues leading the California Zephyr down-grade towards Arvada, Colorado.