Yesss, found it! This was our favorite Monaco cache! Succesfully solved the puzzle at home two months or so before our trip to Monaco. Even though we had the correct coordinates, we needed two attempts and some encouraging from Pouille to finally find this one. The first day we found a small marmelade jar. This is part of another game and is NOT the geocache (future visitors of this cache, be warned!) I knew this, but we couldn't find the real cache. We went back the next day in the evening and finally found it. In the nick of time, as the next morning we had to catch the TGV back to the Netherlands.
We walked to the Palace along the Chemins des Pecheurs down by the sea, took the escalators/lifts up to "The Rock" at the Oceanographic Museum, then followed the Avenue Saint-Martin to the Cathedral. We visited the Cathedral and then continued to the cache. At one point there is a breathtaking view to the Fontvieille harbor. The route we took as described is really beautiful. We really enjoyed it.
Thanks for the great cache and for showing us this beautiful part of Monaco, Pouille! We give this one a well deserved favorite point!