On the walk to our cabin, a little outside of town, I was checking something on OSM, might have been just learning to use it and read it (it has some learning curve when switching from G-maps).
To my surprise, I saw a shortcut/walking path exiting from the road we were walking on. Already used such paths twice that day for a nice shortcut that didn't show up on G-maps. But there was nothing there.
I told my friend that I'd like to check what this strange hacker map is showing. When we looked again, we noticed that there actually was a trail uphill, what at first sight seemed to just be a forested hillside.
As we went up, the trail started to be more evident. We climbed for a couple minutes, went past a cabin with no road leading to it (pretty normal in Norway), and a few more minutes after it we arrived at a semi-top, with a big boulder and a picturesque view out from that viewpoint.
Very cool memory on the last day of the holidays, made possible thanks to somebody marking that trail on OSM.