Railway loop - Sri Lanka

Demodara tunnel and railway entrance referred to as the Demodare Loop, is where the rail line travels around a spiral loop beneath itself and appears out of a tunnel located precisely underneath the Demodare train station. This engineering marvel is the only spiral loop in the world where a tunnel lies under a railway station. Folklore claim the idea was inspired by observing a supervisor in a tea estate unfasten and retie his turban.
Constructed during the colonial era, it was necessary for the transportation of tea produced in the estates of Uva region to Colombo. An innovative track needed to be designed, as engineers and surveyors discovered that with the maximum inclination allowed by the Ceylon Government Railway was one foot per 44 feet (1/44) at the time, the slopes at Demodara were impossible for the track to work out.