The Grand Master of the Militia Templi resides at the Magistral See, Castello della Magione in Poggibonsi (Siena).

At the Magistral See have their seat also the departments (ressorts), which form the Grand Magistery.
 

The Castello della Magione dates from the 11th  century. On the 5th of September 1140 it was donated by Gottifredo di Arnolfo and Arnolfino di Cristofano, heirs of the founders,  to the Monks of the Saint Michael Abbey in Poggio Marturi, who confided it to the Knights of the Temple, becoming, by this way,  one of the numerous "Mansiones" or "Domus Templi" on the via Francigena.

In 1312 the Order of the Templars  was abolished and the Magione was given to the Hospitallers.

The castle,  lowered and reduced into a farm, was bought by several people, among whom  were the Princes Corsini, until 1979, when it was bought by Count Marcello Alberto Cristofani della Magione, who donated it to the Militia Templi, which was just beeing founded, as patrimony and Magistral See.  After the donation the difficult work of restoration of the entire building was started.

The castle maintains evident signs of its romanesque origin, in spite of some changes appeared during the centuries: entering the inner court, where have sight the big halls of the old rooms of the pilgrims and those of the Knights-Monks, everyone gets the feeling of a revival in the heart of Middle-Age.

In Castello della Magione are also seated the Scouts Group  “Valdelsa-Alberto d'Albertis”, the “Academy St. John”, the publishing house “La Magione” and the foundation “Jaques de Molay” for the charitable works of the Templars.