You can now approach the stairs that lead to the last part of the boardwalks, right before the canyon called Desfiladero de los Gaitanes. Stop for a minute to see how far you have got and look back at the path. You have arrived at the place where an old dry canal and El Caminito del Rey separate one from another.

The canal goes underground up to the Eugenio Ribera aqueduct bridge and the suspension bridge. In 2017, the canal was reopened after it had been refurbished. This way visitors could walk along it and use it as an alternative way when the above path cannot be used due to rain, wind or rockfall.

The tunnel is 300 metres long, and it consists of 285m-long underground part and 15m-long way in Hoyo Valley.

It has warning lights inside of it, and small holes all over the ceiling. These are actually old blastholes and small cracks that are now used as a shelter by several species of bats. In order not to bother them, there is only dim light that comes from the LED bulbs installed close to the floor.