On arriving, at first glance, it appears as a humble country church, but once inside, it is amazing.

The walls and vaults are completely covered with splendid frescoes in dazzling colours, depicting moments of religious life.
Unfortunately, photos do not render their beauty.

The American art historian Bernard Berenson (Butrimonys, 26.06.1865 - Fiesole, 6.10.1959) called them "one of the most elaborate decorative schemes of the entire Renaissance".

A bit of history:
In 1468, there was already a small church granted to the Carmelite friars.
In 1501, the foundation stone of the new church was laid.
Between 1515 and 1526, the bell tower was erected.
The consecration took place in September 1528 in the presence of Francesco II Sforza, who had paid for the wonderful fresco cycle.
With the edict of Maria Theresa of Austria in 1772, convents were suppressed and the church and convent underwent a slow decline that lasted until 1864, when the order of the Sisters of the Holy Family took over ownership, restoring the complex to its original splendor.
The authors of the frescoes are Francesco Scanzi, Giulio Campi, and Francesco and Bernardino Carminati.

For more info:
wikipedia: chiesa di Santa Maria delle Grazie
a walk in the city - part 1
San Giacomo church - part 2
Santa Maria Assunta church - parte 3
Sforza fortress - 5