It was much more than a time of artists we eventually named mutant turtles after.
  1. Michelangelo's 'David' is terrified.
    His very nervous expression is only visible from directly in front of him and from above him (and the average viewer will never know): http://goo.gl/bMy025
  2. The Sistine Chapel makes God a brain.
    Michelangelo strikes again! In 'The Creation of Adam', It turns out that the figures of God, His angels and even the soon-to-be-created Eve under His arm form a nearly perfect cross-section of the human brain: http://goo.gl/jptkX5
  3. Da Vinci took a secret selfie.
    In 2009, the art world collectively lost its shit when a potential da Vinci self-portrait was discovered. It was hidden within one of his many scientific papers, a treatise on flight and general ornithology called "Codex on the Flight of Birds." The portrait was so cleverly hidden that it had gone unnoticed for 500 years: http://goo.gl/ECSKaw
  4. Raphael hid a future-building in a painting.
    While working on 'The School of Athens', Raphael had his friend Donato Bramante design "the architecture" for the fresco. Sure enough, Bramante's contribution was a carbon copy of the floor plans for the new St. Peter's Basilica he was working on just down the street. The School of Athens wound up offering a ground-level glimpse at the completed work more than a century before it would be finished: http://goo.gl/iL1Ifj
  5. Renaissance painters depicted UFOs.
    For instance in 'The Madonna with Saint Giovaninno', where it's clear as day behind Mary: http://goo.gl/bMy025