The tunnel of La Engaña was at the time the longest in Spain, 6.976 meters, but it was never used. It was part of a railway project between Santander and Sagunto (Valencia). It linked the towns of Vega de Pas in Cantabria with Pedrosa de Valdeporres in Burgos.

The drilling lasted 8 years, beteween 1951 and 1959. It was mostly used the labor of republican prisioners, housed in barracks of both sides of the tunnel.

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These are the worker’s rooms.