Here's a little Sunday walk from Mariinsky Park to St. Andrew's Church (and back). The final location is somewhere along the way, so you can do the multi either from #1-10 or basically also any other way.
You simply have to go to the 10 waypoints (including the listing coordinates) and look around until you find the spots from the photos. Write down the "hidden" numbers and when you have all 10, do the maths.
Happy hunting!