Besides fixing bugs from ITO World or OpenStreetMap notes I also tend to do some general mapping when I am out and about. Coinciding with my "buying the whisky of the month" event (if you want to contribute to this, see the wishlist ;-) ), we ended up walking past a rather curious building with a park on top in London: Brown Hart Gardens.
The gardens, new café, and the "Duke Street Electricity Substation" that lays underneath were not mapped at all, and of course I could not let that be. From photos and memory, I re-created the gardens in JOSM, my preferred OpenStreetMap editor and now it is available on the map — including the steps and the elevator:
There is also a 3D rendering available: