How do you build a bridge on a mountainside when the grade is so steep that a linear ramp isn’t possible? Build a loop, and if one is not enough, build two. This is what engineers did when the built the Kawazu-Nanadaru Loop Bridge, also known as the Japanese Double loop spiral, in Kawazu, Japan. This double spiral brings cars up and down a full 45 meters while being seemingly suspended in a valley between two mountainsides. The spirals measure 80m in diameter and the whole ramp section is 1.1km long.
The bridge on Highway 414 between Tokyo and the Izu peninsular was finished in 1982 and has become a well known landmark since.