I just wanted to share details of a project to map Nottingham's caves - producing 3D images of the sandstone caves beneath the streets.
There is a much more detailed blog post about it here, which includes a tour of the caves and lots of photos.
More pictures and information are available on the Nottingham Cave Survey website, along with YouTube videos.
Even more exciting is a soon-to-be-released app with augmented reality capability. So you will be able to stand in front of a building in Nottingham & see an image of the caves underneath on your phone! Brilliant!