The tunnel of Cotefablo is a public traffic tunnel located between Broto and Biescas, in Aragon, not far from the Pyrenees, Spain. The tunnel is 683 m long and was constructed in 1935. It was the scenario of a famous tragic accident during the 1989 "Vuelta a España", causing that the brilliant 30-year-old german cyclist, Reimund Dietzen, retired from active sport due to the crash.