photo management - How do I identify the object of a picture I've taken?

Sometimes I have a picture which I don't know, or which I have taken a long time ago. So how do you identify unknown stuff on your image?

For example I saw this picture, and what is the best approach to identify the hill on it?

Answer

I have had some success posting pictures on Flickr asking for help identifying what it is, tagging with anything relevant possible.