A new project called Curious Travellers is asking the public for photographs of cultural landmarks they have visited over the years where those places have since been destroyed or at risk of being destroyed.
http://www.visualisingheritage.org/CT.php
The Locate page has a map of the places they have put on so far. In the UK, there's the Maritime Mercantile City part of Liverpool. In Germany, Cologne Cathedral. Other places are further away but it's quite possible that some of you may have photos of these places.
The site has details as to how to upload photos.
As this website is very new, there's not much to see at this time but that should change as time passes.