Sorry about that. It relates to the use of a filter often mentioned in these forums.
I used the desktop version of Nik Software's Snapseed program.
One of the features of Nik Software ( Color Efex Pro , Silver efex etc ) is the ability to add filters selectively by adding Control Points to the image.
I just added a control point over the dark interior and raised the brightness a little , nothing more.
Nik filters can be as easy or complex as you want.
Definitely worth giving them a look or a free trial.