This is a brief list of what, in my opinion, is well worth seeing in Milan. Being a summary, it's not exhaustive and it is, obviously, influenced by my tastes and interests.
But I don't want to replace a tour operator: I just offer some guidance to those who, perhaps unexpectedly, have a few free hours or a day not scheduled on the agenda.
A short walk from the B&B
Le Colonne di San Lorenzo (Columns of San Lorenzo). Vestiges of imperial Milan, they are sixteen marble columns, around 7.5 meters high with Corinthian capitals. Find more information on Wikipedia.
Basilica di Sant'Ambrogio (Basilica of Sant'Ambrogio). It is one of the oldest churches in Milan, dating back to the early Christian Era and the Middle Ages. Find more information on the official website and on Wikipedia.
Università Cattolica Del Sacro Cuore (Catholic University of the Sacred Heart). Founded in 1921, it is a private Italian-inspired Catholic, whose headquarters are worth a visit even for simple tourism. Find more information on the official website e su Wikipedia.
Museo Nazionale della Scienza e della Tecnologia "Leonardo Da Vinci" ("Leonardo Da Vinci" Museum of Science and Technology). It is the largest museum of science and technology in Italy and one of the most important in Europe and the world. Find more information on the official websiteWikipedia
Duomo (Milan Cathedral). The Milanese church dedicated to St. Mary of the Nativity. It is the main landmark of Milan. It is the fourth cathedral in Europe by area. Find more information on the official website e su Wikipedia.
Navigli (The Navigli canals). Once an area of common people, today is famous for its cultural and night life, with its numerous restaurants, bars and nightclubs.
Castello Sforzesco (Sforza Castle). It was built in the 15th century by Francesco Sforza over the ruins of a previous fortification. It is one of the largest castles in Europe, home to important cultural institutions and a popular tourist destination. It is placed next the Parco Sempione, the central park of Milan, often home to musical and cultural events. Find more information on the official website e su Wikipedia.
Piazza della Scala (La Scala Square). Connected to Piazza Duomo (Duomo Square) from Galleria "Vittorio Emanuele" ("Vittorio Emanuele" Gallery), it is one of the most famous sites of Milan, mainly because of the presence of the famous Teatro alla Scala. The square also provides the entrance to Palazzo Marino (the back, actually), seat of the Municipality of Milan, and the monument to Leonardo da Vinci. Find more information on Wikipedia.
Pinacoteca di Brera (Brera Art Gallery). It is a national gallery of ancient and modern art, whose museum houses one of the most famous collections of Italian painting, especially Veneto region and Lombardy. Find more information on the official website e su Wikipedia.
Palazzo Reale (Royal Palace). Located next to the Duomo, it has long been the seat of government of the city of Milan. Today it is home to exhibitions, and a cultural centre of the Lombard capital. Find more information on the official website e su Wikipedia.
Cenacolo Vinciano (The Last Supper). Located in the church of Santa Maria delle Grazie. The renowned painting made by Leonardo da Vinci, it is the most famous version of the Last Supper of Jesus. It is located in the former refectory of the convent adjacent to the sanctuary of Santa Maria delle Grazie in Milan. Find more informationon the Last Supper and the one on Santa Maria delle Grazie.
Piazza Gae Aulenti (Gae Aulenti Square). A circular square with a diameter of 100 meters, it was dedicated to the architect and designer Gae Aulenti in 2012, after the works of redevelopment of the whole area. It offers a particular view of the new profile of Milan, with its new skyscrapers. You can find more information on Wikipedia
Abbazia di Chiaravalle (Chiaravalle Abbey). The Abbey is a Cistercian monastery, founded in the 12th century by Saint Bernard of Chiaravalle as an offshoot of the Abbey of Cîteaux. The church is one of the first examples of Gothic architecture in Italy. Find more information on the official website e su Wikipedia.
Abbazia di Morimondo (Morimondo Abbey). It is a Cistercian Abbey whose architecture has however moved towards the Gothic style. You can find more information on Wikipedia.
Parco del Ticino (Ticino Park). Formed by the Natural Park of Ticino Valley in Lombardy and the Natural Park of the Ticino Valley in Piedmont, it offers numerous natural, artistic and urban attractions. Find more information on the official website e su Saltainsella
Milan-Trezzo sull'Adda pedestrian and cycle path. The pedestrian and cycle path runs for about thirty kilometers along the Naviglio Martesana and offers many characteristic views. Find more information on Saltainsella website.