The Castello De Piro al Grumello, generally known as Grumello Castle, owes its name to the rocky hump (grumo) on which it is located. It was built between the end of the Thirteenth and the beginning of the Fourteenth century by the ghibelline De Piro family. Thanks to its strategical position the castle overlooks the city of Sondrio and a wide section of Valtellina.  
The castle consists of two buildings surrounded by walls. The first building, on the Western side, probably had a residential purpose, as proven by the remains of a fireplace room. The slits in the walls suggest the presence of a gatehouse. 

The second building, on the Eastern side, clearly had a defensive purpose, as proven by a high watchtower.

The castel was destroyed in 1526 by the Grisons, the original structure was much wider than the current one, as evidenced by the archaeological excavations that are currently taking place. The Grumello castle belongs to FAI (Italian Fund for the Environment) and recently underwent renovation works.