(ANSA) - Siena, March 3 - Siena's 13th-century cathedral will reopen its "stairway to heaven" shortly, local authorities said Tuesday. The famous black-and-white striped cathedral first opened a series of spiral staircases to the public in 2013, allowing visitors to climb up to a walkway near the top of the 16-metre nave. Once they have reached the top of the spiral staircases, visitors can enjoy an aerial view of the inlaid marble mosaic floor, one of the most ornate of its kind in Italy.

The mosaics created by some 40 artists from the 14th to the 16th centuries are laid out in 56 panels shaped like rectangles, hexagons and rhombuses in different sizes, and cover the entire floor of the cathedral with pictures of the sibyls, allegories and virtues, and scenes from the Old Testament.

From the top of the staircase, visitors can also get a closer look at the cathedral's hexagonal dome with its '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 interior striped columns and walls are made from black and white marble in a nod to Siena's black and white coat of arms. The capitals of the columns in the west bays of the nave are sculpted with allegorical busts and animals, while the horizontal moulding around the nave and the presbytery contains 172 plaster busts of popes dating from the 15th and 16th centuries, starting with St. Peter and ending with Lucius III. The spandrels of the round arches below this cornice exhibit the busts of 36 emperors.

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 a high-impact series of very colorful frescoes painted by Pinturicchio, probably based on designs by Raphael.

They tell the story of the life of Siena's favourite son, Cardinal Enea Silvio Piccolomini, who eventually became Pope Pius II, while the ceiling is covered with painted panels of mythological subjects executed between 1502 and 1503.