Gian Giacomo Poldi Pezzoli lived from 1822 to 1879 and spent the second half of it turning his mother's apartment into a set of rooms each designed around what would hang in it — from 1846 he had Giuseppe Bertini and Luigi Scrosati decorate them one by one, so that a room and its contents would agree. He left the lot to the Brera Academy, and Bertini opened it to the public on the 25th of April 1881. The whole institution is therefore two years younger than the man who assembled it, which is unusually quick work for a bequest.
Then in August 1943 the air raids came and took the ceilings, the stuccowork, the frescoes, the glass. The paintings had been moved to safety; the house had not. What you walk through today was rebuilt after the war on the explicit principle of putting it back where it was and as it was — and the seam shows if you look for it, because one room escaped. The little Dante Study that Bertini and Scrosati painted between 1853 and 1856 is the only surviving piece of the original painted decoration in the building. Everything else in this house is a very careful act of memory.
I have been twice, both times on a flat winter morning, and both times found the armoury empty of anyone but a guard. It is worth saying plainly that this is not a large museum and does not behave like one: you can do it properly in ninety minutes and leave with four or five things you will still be thinking about at dinner. Skip nothing on the way up the stairs. The stair is part of the collection.
In one night in August 1943 Milan lost most of its museums. This one it decided to build again.
The raids took the ceilings, the stucco, Bertini's painted glass, the frescoes and the damask on the walls of the Golden Room. The collection itself had been carried out and hidden beforehand — which is the whole reason there is anything left to argue about. The building reopened in 1951.
Fernanda Wittgens and Ferdinando Reggiori set the terms of the rebuilding: save what could be saved, replace the rest honestly rather than pretend. So the Golden Room's ceiling is a lighter answer to the gilded one that burned, and nobody hides that from you. It is a reconstruction that declines to lie.
Which is why I would send you to the Dante Study last, when you know what you are looking at. It is a small painted room and it is the only one Poldi Pezzoli himself would recognise. Stand in it for a minute longer than feels natural.