Palazzo Madama is in the heart of Turin, right where it was supposed to be the Roman castrum (the geographical centre of the city) and it rises on what in the Ancient Rome was called Porta Decumana. At the beginning of the 1st century the city entrance was from the side of the Po river that, due to its strategic position, had to be carefully defended: after the fall of the Roman Empire, the Porta Decumana was transformed into a fortress to defend the city.
During the centuries the fortification of the Porta Decumana passed to the Savoy-Acaja (younger branch of the Savoy) which in the first half of the 15th century widened it into a castle. After a century, a member of the Acaja (Lodovico) reworked the castle, giving it the squared shape with the court and the arcades, the four cylindrical angle towers, that today can still be recognized on three sides. The extinction of the branch of the Acaja led to the castle becoming a residence for the Savoy’s guests.
It was occupied for a short time by Emanuele Filiberto of Savoy, who wanted to make it a residence for dukes after moving the capital from Chambéry to Turin. Considering the Palazzo Reale more suitable for himself, decided to re-establish Palazzo Madama as the building for guests.
In the following century, it was considerably embellished during the regency of the two Royal Madams (Maria Cristina di Borbone-Francia e Maria Giovanna Battista di Savoia-Nemours), the old Middle Age castle was retrained thanks to the first architect of the Savoy House, Filippo Juvarra: the big façade is his.
Palazzo Madama became house to the Museo Civico d'Arte Antica in 1934, and during the 20th century has undergone many renovations which terminated at the end of 2006 giving back to the city an important document of its two thousand years of history.
(source: www.wikipedia.org)