Freemasons' Hall in London is the headquarters of the United Grand Lodge of England and the Supreme Grand Chapter of Royal Arch Masons of England, as well as being a meeting place for many Masonic Lodges in the London area. It is located in Great Queen Street between Holborn and Covent Garden and has been a Masonic meeting place since 1775. 
Parts of the building are open to the public daily, and its preserved classic Art Decostyle, together with its regular use as a film and television location, have made it a tourist destination.
 
Interesting facts...
While conspiracy theories often link Masonic symbols—such as the “all-seeing eye”—to global control, members state these icons are intended to represent the “Great Architect of the Universe” watching over them, rather than anything sinister.