The large square looking onto the Castle’s current structure was built during the second half of the eighteenth century, when (in 1763) the estate of Agliè was purchased by the Savoy household as an appanage for the Duke of Chiablese, Benedetto Maria Maurizio, son of Carlo Emanuele III and his third wife, Elisabetta di Lorena.
The acquisition of the Castle by the crown led to the need for a renewed and strengthened expression of magnificence and this task was entrusted to Ignazio Birago di Borgaro.
The architect concentrated his actions not only on the structures of the Castle but also on all the urban space in front of it, including the parish church, creating the Town – Castle relationship which is still exists.
The newly found royal dignity taken on from the already splendid residence of the San Martino family of San Germano required not only the renewal and extension of the seventeenth century structure, but also the creation of a large court of honour overlooking the town.
A "court" capable of welcoming the chosen son of the Sovereign and the royal corteges.
Up to the mid eighteenth century documents certify the presence of a second courtyard, towards the town, built up on all sides.
With the Castle behind, to the right was the current wing with the pillared atrium (now the entrance and ticket booth to the Castle); to the left a gallery wing, which was much shorter than the current one.
Towards the town the courtyard was closed by two buildings with a central passageway, which led to the bridge over the Rio.
In actual fact the separation of the Castle from the town was clear and this was perhaps a reason for the initial defence problems.
When creating this project, Ignazio Birago demolished all the seventeenth century features, except for the right hand wing. He filled the Rio, thus doubling the surface area of the square.
The parish Church, dedicated to Santa Maria of the Annunciation and late Gothic in style, was also in the pathway of his plans, as it had significant static problems.
The church faced with the apse towards the west and the main axis was perpendicular to the direction of the porticoed street.
The religious building was demolished and the new building was built in such a way as to position the façade as a fifth of the new square. It was more or less in the position already indicated approximately a century previously, in the table of Agliè of the Theatrum Sabaudiae, almost as though to confirm a position that is already well determined from an ideological point of view.
Confirming the relationship between the Castle and the Church was the creation of a lengthy connection body over two floors, which leads from the interior of the Royal Apartments to the apse located opposite the façade of the Church. This was a spectacular suspended route reserved for the sovereign and his entourage in order to attend religious functions; it is still called "Galleria alla Tribuna" today.
The structure, which is unique in the region, is an exception on a wider territorial scale also. It is a synthesises a variety of functions and became a formal fundamental element in the definition of the new "place royale".
A connection element between the church and the castle, spiritual and temporal power, similar to what was already created by Vittorio Amedeo I in the capital, the gallery is similar to the connection between the Cathedral and the Royal Palace of Turin, through the Shroud Chapel.
A symmetrical body to the Gallery, it was meant to close the square on the right side, but Birago’s plans were not completed and only the attachments of brick remain of this second Gallery, which is incomplete yet legible on the front of Palazzo Birago.
The square was completed by the two Pavignano buildings (alongside the Church, but in a position which is further back) and Birago on the opposite side.
From the second half of the nineteenth century the square was accessible from the tree-lined avenue, which divides the Castle from its Park.
The square was restored recently; returning to a scheme that was already present in the historical documentation and which allowed for the Castle to be linked better to the axis of the main street, via Tommaso.
The Monument to those who died in the First and Second World Wars rises up at the summit of the tree-lined avenue, alongside the square.