The square tower was built around 1320 on the ruins of the old castle by Marquis Teodoro II of Monferrato, as a defensive cornerstone in a system including Montemagno, Casorzo Grazzano, Moncalvo, Rinco and Vignale in the North, Lu, Camagna and San Salvatore in the South. A fortified line of hills meant to protect from the near Visconti, Lords of Milan, of which remain important traces. The so-called “tower of the signals”, is the result of layers of later interventions on the original construction. The most important of these, which occurred approximately in the middle of the Nineteenth Century, coincides with the realization of a lining of bricks, on the four sides of the tower, in order to fill and heal the pre-existing masonry. Note the slightly protruding part, with four comedians-head (a recurring decoration in other towers on the same age) and the Ghibelline battlements (a sign of fidelity to the empire). The building is completed by the near gatehouse. The tower, completely restored in recent years, is open to the public. Viarigi will be the start of a new Turris route through Monferrato.