This series of 5 pictures are the second part of the Hadrian's Wall photos.  I visited 2 sites, Vindolanda and Birdoswald.  Both of these are forts and both are no more than 'hip high' with respect to what remains.  I've read it wasn't until after the Norman invasion that the large scale dismantling of the wall started.  The easily gathered, finely shaped stones were a source of excellent building material necessary for the architecture and building techniques the Normans brought with them.  It's ironic the quality and strength of the wall material is what ultimately lead to it's destruction.