Oregon Vortex, Optical illusion attraction in Gold Hill, Oregon, United States.

Oregon Vortex is a tourist site in Gold Hill, Oregon, built around a tilted structure that once served as a gold assay office. Balls appear to roll uphill here, and visitors seem to grow or shrink depending on where they stand.

The Old Grey Eagle Mining Company built a gold assay office here in 1904, which later slid off its foundation. The slanted building became the basis for the present-day tourist attraction.

Local legend holds that Native Americans called this ground "forbidden" land, and travelers passing through would find their horses refusing to go on. The story predates any construction at the site, including the assay office built in 1904.

The attraction is closed after Sardine Creek flooded in March 2025, sending water, mud and debris through the property and damaging structures; the owners aim to reopen in March 2027. The entrance sign stands among trees on Sardine Creek in Gold Hill, off Interstate 5 north of Grants Pass.

Researchers attribute the optical illusions to orientation framing, where the brain compares irregular angles against horizontal reference points. Visitors experience these illusions most strongly when standing inside the tilted building and using the outdoor environment as a reference.