It has 564 rooms and 75 staircases although only 23 were used frequently. There is a fireplace in each room. There are 100 bedrooms.
The "Salle des États Généraux", built in the beginning of the 13th century, is one of the oldest seignoral rooms preserved in France, and is also the largest remaining civilian Gothic room. The room was used as a court of justice by the Counts of Blois, and was used in 1576 and 1588 for the "États Généraux".
The medieval castle was purchased in 1391 by Louis I, Duke of Orléans, brother of Charles VI; after Louis' assassination, his widow, Valentina Visconti, retired to this castle at Blois. It was later inherited by their son, Charles d'Orléans the poet, who was taken prisoner at Agincourt and spent twenty-five years as a hostage in England, before returning to his beloved Blois, which he partly rebuilt as a more commodious dwelling. It became the favourite royal residence and the political capital of the kingdom under Charles' son, King Louis XII. At the beginning of the 16th century, the king initiated a reconstruction of the main block of the entry and the creation of an Italian garden in terraced parterres that occupied the present Place Victor Hugo and the site of the railway station. In 1890 the construction of the Avenue Victor Hugo destroyed the remainder of the gardens.
This wing, of red brick and grey stone, forms the main entrance to the château, and features a statue of the mounted king above the entrance. Although the style is principally Gothic, as the profiles of mouldings, the lobed arches and the pinnacles attest, there are elements of Renaissance architecture present, such as a small chandelier.
When Francis I took power in 1515, his wife Queen Claude had him refurbish Blois with the intention of moving to it from the Château d'Amboise. Francis initiated the construction of a new wing and created one of the period's most important libraries in the castle. But, after the death of his wife in 1524, he spent very little time at Blois and the massive library was moved to the royal Château de Fontainebleau where it was used to form the royal library that forms the core now of the Bibliothèque nationale de France.
In this wing, the architecture and ornamentation are marked by Italian influence. At the centre is the monumental spiral staircase, covered with fine bas-relief sculptures and looking out onto the château's central court. Behind this wing is the façade of the Loges, characterised by a series of disconnected niches.