Confusion Hill is a roadside attraction in Piercy, California. The attraction, which opened in 1949, includes what is dubbed as a "gravity house," a structure built to give the interior visitors tilt-induced optical illusions, similar to the perspective on a gravity hill. Occupants experience the need to stand upright when they actually already are.
For 60 years, Confusion Hill was on the heavily traveled US 101 highway, also known as the Redwood Highway. Due to repeated mudslides obstructing the road, US 101 was realigned in 2009 to the Confusion Hill Bridges, bypassing the attraction. In 2010 Confusion Hill was granted California Points of Historical Interest status.