Help Needed - Trying to extract/isolate a photo reflection visible on a glass window

To anyone out there who might have a solution to my problem - I'm trying to extract/isolate a reflection shown in a photo; the photo was taken from the inside of a building, capturing the outside scenery through a glass window.  I'm working on an art project and I want to extract/isolate the reflection that can be seen on the glass window as a separate image in itself (barely visible) - i.e., showing the background inside the building from where the original photo was taken.

I've attached a sample photo I found online - although I haven't been able to find any clear/easy steps I can follow to accomplish this.  Does anyone have any photo adjustments/filters/other editing tools to suggest that can help with this?  Much appreciated!