Palazzo Sansedoni is the most representative building of private architecture of the fourteenth century for its size, adherence to Sienese styles and dominant position between Piazza del Campo and the Via Francigena. It was founded by a family of Ghibelline origin dedicated to banking and strongly involved in the political life of the city. Around 1243 the ancient tower was erected which, together with the tower house, completed in 1339 by a group of builders headed by Agostino di Giovanni in Gothic style, represented a structural unity in the use of bricks right from the foundation. The majestic brick façade on the Piazza dates back to an eighteenth-century renovation in neo-Gothic style by the architect Ferdinando Ruggieri .
Following the family's purchase of the adjacent buildings, three different buildings were aligned , giving rise to the current one with its particular curvilinear façade, which follows the shape of the square. In 1760, the Sansedonis filed two reports stating that the renovation work in the adjacent building had caused structural damage to their building, particularly to the tower. Between investigations and reports, the idea was to safeguard the tower as a family, citizen and civic symbol: however, the family had to accept the provisions of the Biccherna court which, on 17 March 1760, asked for the tower to be demolished . The destruction began in April and was completed in October: a covered terrace was built on its base, which is still accessible today and from which you can admire a beautiful panorama of the city.