The picture below is a trigger for an augmented reality overlay, showing how the ditch at Avebury Henge has silted up over the past 4,500 years or so.
To see the augmented image, go to the App store on your Apple or Android tablet or phone and download the Aurasma app. Register with a username, password and email address, and then press on ‘discover auras’ and search for lizfal. Press on ‘follow’ and then press the small purple square at the bottom of the page. Your camera viewfinder will open. Find the image in your viewfinder and hold still for a few seconds – you should see the augmented image appear! You have to have a wireless connection or 3G active to be able to see the augmented image.