While Duomo is famous worldwide, the most important religious church in the city is actually the Basilica di Sant'Ambrogio.
Sant'Ambrogio (Saint Ambrose) was bishop of Milan during the last few decades of the 4th-century, and he's the city's patron saint.
The Basilica is one of the finest examples of Romanesque architecture. It was originally built as the 'Basilica of the Martyrs', but later reconstructed in Romanesque style.
Inside the church are located the relics of Saints Gervasius, Protasius, and Ambrose himself, just beneath the altar.
The Basilica di Sant'Ambrogio is an absolute must-visit in Milan, it's one of the most important places in the city.