The picture doesn't work but the passage is open with a high ceiling and there is copper sticking up out of the ground in the middle of the passage. If you look up you can see the 2 sides of the passage that you can't get to on either side of the passage. I haven't played since first getting into Venice after killing the first boss so I can't get back there to take a screenshot.
PS. You get to the area from the main entrance to the mine by going straight to the first 3-way intersection and taking the right path and just keep going along this path till it opens up to a wider passage at the top left side of the map. If you look up as you go through that passage you should see the 2 sides of the passage and it should show up on your map.
you can also get there from the village. climb a ladder, the only one you find, and go forth, climbing when possible. Just one time you have to go down. Finally, you move from the roofs to an "alley" and in the end you find an entrance to the mine. It's locked, but if you have a hammer, you already know what to do. I guess it can be useful to get back into the village in a later quest, but I am just begining yet.