This is the Metroon. http://www.bbc.co.uk/blogs/bbcinternet/2011/10/digital_public_space_idea.html for details
http://commons.wikimedia.org/wiki/File:Alexandra_Palace_mast.JPG The transmission mast above Alexandra Palace, where BBC Television began broadcasting from its studios there in 1936. Uploaded to illustrate BBC One. Taken by me, Paul Hayes, in September 2001.