Once they have reached the top of the spiral staircases, visitors can enjoy an aerial view of the medieval and Renaissance mosaics that cover the marble floor, as well as getting closer to its hexagonal dome with 'trompe l'oeil' coffers painted in blue with golden stars and topped with Bernini's gilded lantern.
The Gothic cathedral built between 1215 and 1263 is a treasure trove of art, and home to works by the likes of Donatello and Michelangelo.
Its distinctive striped columns and walls are made from black and white marble in a nod to Siena's black and white coat of arms. The "stairway to heaven" reopens this year on March 9 through October 31 for guided tours of the cathedral and its adjoining Piccolomini Library.
The latter houses precious illuminated choir books and frescoes painted by Pinturicchio, probably based on designs by Raphael.
















