On May 1, 1913, the so-called fish train began to travel through a 40-meter tunnel under the center of Vigo. This tunnel was built as the need for transportation between the O Berbés fish market and the station arose. of Urzaiz train, to transport goods from the port to other cities. Its tunnels still remain under the center of the city, but not currently used.

Another tunnel will begin to be built in a few months in the center of Vigo and will go from Policarpo Sanz Street to the middle of Elduayen Street and will be from both directions to streamline traffic and allow pedestrianization of the Puerta del Sol.

Under the walls of Lugo, declared a World Heritage Site and unique in being preserved, a tunnel of medieval origin allowed the channeling of wastewater, this located inside the cube VI.

Much has been said about the tunnels under the City of Knights: Betanzos in A Coruña. It seems that there are accesses to them in different houses in which when opening a door one finds access to a tunnel and not to another room.

It was speculated on with the name of the church located in the city and with which the tunnels flowed: Santa María de Azogue comes from the meaning The plaza of a town where there is no commercial deal and Azogue origin, being close to the mines of Azogue since it was the old name given to the mercury extracted from cinnabar and used by the alchemists. That he believed that mercury was a basic ingredient to get the philosopher’s stone and with it, that he could cut the metal, cure diseases and grant immortality. The hatters also use it for the skin to the high toxicity of it.

It has been found that mines of this metal were found in the year 1765 and that 10 years later in 1785 several mouths of mines were opened by a Royal Order to the Intendant of Galicia to search for cinnabar veins without finding it.
The mystery of his travels remains underground for the moment waiting for someone to discover them.