Prominent features in the historic centre of Invorio Inferiore are the Visconti Tower and the remains of an ancient castle, which stand on a hill overlooking the town.

The existence of these fortifications was documented as early as the year 1000; in the 13th century they became the property of the Viscontis, who ruled over the town for centuries. The castle was destroyed during the war the Viscontis fought against the Marquis of Monferrato for possession of the Novara area, and was not rebuilt; today only some isolated parts of the fortifications remain, including the well-preserved crenellated tower, within a large private park.

The square tower, 17 metres high, is made of well-shaped dark grey stone blocks. On the lintelled entrance doorway is an prominent marble tablet with the coat of arms of the family: a snake swallowing a child, with heraldic caltraps. A few narrow windows open into the sides of the tower; the interior, once divided into three floors by wooden platforms, has a fine barrel vaulted ceiling. The top of the tower above the stone gutter displays the characteristic swallowtail crenellations.

The tower is surrounded by the remains of the castle and its two encircling walls.