Bernini's Scala Regia

The Scala Regia is a ceremonial staircase leading from the narthex of St. Peter's Basilica to the papal apartments in Vatican City.  The staircase was built by Antonio da Sangallo in the early 16th century, and was restored by Gian Lorenzo Bernini from 1663 to 1666.  The area dedicated for the stairs was very narrow, so Bernini had trouble designing.  He reverted back to optical illusions because he did not want the stairway to seem small.  The optical illusion he used was perspectival diminution in which the objects appear different that what they are.  As you ascend the stairs of the Scala Regia, the walls become more narrow, the column diameters are smaller, and the distance the columns are from the walls is much shorter.

Scala Regia