The Duomo di Siena, also known as the Cathedral of Siena, is a magnificent medieval church located in the city of Siena, Tuscany, Italy. It is considered one of the greatest examples of Italian Gothic architecture and is a UNESCO World Heritage Site.

Construction of the cathedral began in 1215 and continued over the course of several centuries, with the final touches being added in the 19th century. The exterior of the cathedral is adorned with black and white marble stripes and intricate carvings, while the interior boasts an intricate floor made of inlaid marble, stunning frescoes by some of Italy's most famous artists, and a stunning bronze pulpit by Nicola Pisano.

One of the most notable features of the cathedral is the Libreria Piccolomini, a small library that houses some of the finest illuminated manuscripts from the Renaissance period. The cathedral also contains several other treasures, including works by Donatello, Bernini, and Michelangelo.

Visitors can climb to the top of the cathedral's dome, which offers stunning views of the city and the surrounding Tuscan countryside. The cathedral is also home to the Museo dell'Opera, a museum that houses the original statues from the facade of the cathedral, as well as other important works of art.