Dedicated to the city's patron saint and one of the oldest churches in Milan, its core dates back to the early Christian period (379- 386) and was later transformed into the Romanesque basilica we know today in the 11th century. It has retained its layout with three apsidal naves without a transept and with a four-sided portico in front, and a gabled façade with a characteristic brick colour and inserts of white plaster of local origin. One of the special features of the architectural layout is the design of the light, which comes mainly from the large windows on the façade, and its ability to transform the perception of the interior space, accentuating its monumentality. In the square, on the left side of the basilica, there is a Roman column, which the Milanese call 'the devil's column'. Legend has it that during a fight between Saint Ambrose and the devil, the latter pierced the column, creating the two holes that can still be seen and from which it is possible to hear the sounds coming from hell accompanied by the smell of sulphur.