I have always found buildings covered in vegetation intriguing. Seem to remember more than a few horror films as a kid with creepy buildings covered in vegetation that bad things happened in. Maybe they had more of an influence than I would like to admit. Not hard to find them, just keep wandering around and you will come across them. If you can't find any where you are, head to New England, seems like all the colleges there have a few. The image at the top was down an alley in Sag Harbor, NY. The bottom image is from a walk around Amsterdam.