The history of Oleggio Castello and its Castello, which belongs to the Marquis Dal Pozzo d’Annone and his family, stretches back for over a 1000 years. In fact, in the year 900 AD, the remains of a Roman Castrum, campsite of the Vth Legion, were unearthed.
The Castrum became known as the Q.Legio, successively converted into Olegio, Olezo and then in the year 1186 into Oleggio Castello, in honour of the Castello built around the year 1000, by the Visconti family. It was from here that the Visconti, around the year 1200 made their move on Milan, over which they reigned supreme from the year 1277 until the death of Filippo Maria in 1447. His only daughter, Bianca, married Francesco Sforza who succeeded to his father-in-law. In the following centuries, the Castle was more or less abandoned, and allowed to fall to rack and ruin.
It was not until the second half of the 18th century that the descendants of the Visconti reclaimed the castle, turning the ruins into a residential Palace. In the intervening centuries the Visconti had added to their title the suffix d'Aragona, granted by King Alfonso of Naples and Sicily, in 1442. The last of the Visconti d'Aragona, Marquis Alberto Visconti d'Aragona, was involved in the nascent struggle for Italian independence from under the dominion of the Hapsburg Empire, known as the "moti carbonari". In 1830 he was condemned to death and stripped of all his possessions. They passed to his sister Virginia, wife of Bonifazio Dal Pozzo d’Annone, originally from Rovereto, later call Alessandria, in honour of Rolando Bandinelli, who became Pope Alessandro III in 1167.
His son Claudio (1839-1885) connoisseur and lover of art and architecture, and heavily influenced by the Arts and Craft Movement originating under William Morris in England, redesigned and rebuilt the Palace, laying out a spacious Park at the same time, thus transforming the ancient walls into a grandiose neo gothic Victorian castle, said to be "one of the purest reinterpretations of neo-gothic Tudor existing in Italy.
Across the road lies the modern day Palazzo Visconti, where Alberto Visconti d’Aragona lived out his remaining years after having been pardoned for his participation in the “moti carbonari” He died in 1885 and is buried, together with his wife, Lady Luigia, marchioness of Monticelli Obizzi, in the cemetery in Oleggio Castello
During successive World Wars the Palazzo was converted into flats for local inhabitants. When Oleggio Castello became an independent Parish, separating from Paruzzaro, the Palazzo temporarily became the local elementary school. In more recent years the building was largely abandoned and fell into disuse. However, it has now been completely rebuilt and has opened as a luxury boutique Hotel, destined to put Oleggio Castello on the international tourist map.
Thus for more than 6 generations, the entire property has belonged to the Dal Pozzo family, and is still the principal family seat.

Ministerial Decree for Cultural and Historical Activities in accordance with LR 1 June 1939 and successive Law no 241/1990 and amendments as per DL 42/2004 and with the mention of “being of particular cultural importance – as a National Monument

..Castello: decree 01/08/1994 signed by Minister Fisichella
..Palazzo: Prot 1898 and 18/05/2011 signed by the Super Intendent architect Luisa Papotti.