The member of the Farnese family who commissioned the Palazzo Farnese went on to become Pope Paul III not long after, so the building got even more palatial soon after it was done. The Farnese family were well-known sculpture collectors - parts of their collection make up Naples’ archaeological museum and Capodimonte Museum today.
Although the Palazzo Farnese is the French embassy in Italy, there are tours available - which is good, given the art that remains in the palace, including frescoes on walls and ceilings. Even if you don’t go inside, you can see some of Michelangelo’s handiwork on the facade. The Renaissance master is responsible for, among other things, the central window that served as a focal point and something of a stage for Pope Paul III when he stood on the balcony.