Spain 's ' '' most dangerous path '' due to reopen this month after extensive reconstruction efforts . The tunnel was built in the early 1900s by a Spanish engineer named Juan de la Cierva, who used it as an escape route from his prison cell at El Escorial Palace on Spain's
Spain 's ' '' most dangerous path '' due to reopen this month after extensive reconstruction efforts . Originally built in the 1900s , the trail 's boardwalks deteriorated over time , forcing the local government to close it .