Colosseum Vault
The Colosseum Vault was a Vault created by Those Who Came Before located in Juno's Temple (which is underneath the Santa Maria Aracoeli). The vault was created to store the Apple of Eden on an erected pedestal at the center of a large chamber.
To enter the Vault's central chamber, one must speak aloud the number "72." After this, the tall pedestal can only accessed by jumping on a series of thin platforms and levers that appear to activate when a person with certain DNA, such as Desmond Miles or Ezio Auditore, touches them. After activating all platforms, a set of stairs rise to form an easy path to the Piece of Eden.
Visitors
The earliest known visitor of the Colosseum Vault was Brutus Cassius, as evidenced by the 4th Scroll of Romulus. Brutus also made a drawing of the Vault, as well as the pedestal holding the Piece of Eden.
The next known visitor was Ezio Auditore, who knew the password to enter, (although how he knew has not been explained). He then put the Apple of Eden on the pedestal and left.
The latest known visitors were Desmond Miles, Lucy Stillman, Shaun Hastings and Rebecca Crane; who figured out the password from the writing Ezio left in the Villa Auditore. After Desmond activated the stairs and walked up to the Apple of Eden, symbols appeared around all of them. Upon touching the Apple, Desmond lost control of himself and was forced him to stab Lucy in the abdomen.