The Tehachapi Loop is a remarkable 3,779-foot spiral, or helix, on the Union Pacific Railroad's Mojave Subdivision, winding through Tehachapi Pass in the Tehachapi Mountains of Kern County, south-central California. The line connects Bakersfield and the San Joaquin Valley to Mojave in the Mojave Desert.

Rising at a steady two percent grade, the track climbs 77 feet in elevation while completing a 1,210-foot diameter circle. One of the most fascinating things about the loop is that any train long enough to span it will actually pass over itself as it goes around. At the bottom of the loop, the track passes through Tunnel 9, the ninth tunnel built as the railroad worked its way east from Bakersfield.