The Portal looks a lot different in a picture then with the naked eye. I think I will need more contrast for it to show up on net. I believe if the mortar joints were darker that may be what is needed.
Yogi,
That looks wonderful. Another success for you and your methods. Those old tunnel portals kept getting darker and darker over the years caused mostly I think from accumulated smoke. This was especially true in the joints where the scouring effect of rain was minimized.