Now that we were sure that there was a ventilation shaft, we went inside the tunnel once again to get pictures.
This is a view of the tunnel roof – the dark object in the center is the ventilation shaft. The brown objects on the roof are probably roosting bats. One of them guys is flying around, near the top of the picture. The white spots on the roof are the eyes of the bats as they watch us approach. At this point, the distant crown of the tunnel end was black with the flying bats as they tried to put a distance between themselves and the tunnel intruders.
You are specifically requested not to enter the tunnel - apart from the danger, you would be scaring the bats unnecessarily.
Please remember that these are shy, harmless creatures that have a very important function in the pollination of flowers and fruits. We share genes with them - they are mammals !