There is purported to be a vault within a chapel in England or Scotland (Rosslyn Chapel?) that contains a code alluded to in some of da Vinci's work. It is written about in a book by Dan (?) Brown.
"An Unbroken Code There exists a chapel in Great Britain that contains a ceiling from which hundreds of stone blocks protrude, jutting down to form a bizarre multi-faceted surface. Each block is carved with a symbol, seemingly at random, creating a cipher of unfathomable proportion. Modern cryptographers have never been able to break this code, and a generous reward is offered to anyone who can decipher the baffling message. In recent years, geological ultrasounds have revealed the startling presence of an enormous subterranean vault hidden beneath the chapel. This vault appears to have no entrance and no exit. To this day, the curators of the chapel have permitted no excavation.
da Vinci's Vault is also an on-line store containing 3,000,000 items.
That's all I can find at this time, Mary.
PS There is also a drawing of his that shows a man inside a circle with his arms upreached. I believe that was pertaining to 'the vault of the heavens' or something like that. I don't recall the name of it or I'd post a link. S'all I got for now.