Not so long ago, in Plymouth, England, Jerry Sibley discovered a Jewish cemetery that dated back to the 1700s. Sibley went to Google Maps, with a clue that placed the older cemetery on Lambhay Hill. After an initial effort failed to find it, he painstakingly over aerial images again until he found bright green spot. He zoomed in—and he could just make out some headstones.
The cemetery had gone unvisited for so long that no one at the synagogue knew how to open the door to the walled space. Sibley sorted through a box of 300 keys until he found the right one. When he opened the door he found a secret garden of trees, grass, flowers, and gravestones.
You can read the full story in an article by Sarah Laskow in the Atlas Obscura web site at: http://www.atlasobscura.com/articles/plymouth-jewish-cemetery-rediscovered.